Discordance of HER2-low Status between Breast Primary and Distant Metastases with Clinical-pathological Correlation

Discordance of HER2-low Status between Breast Primary and Distant Metastases with Clinical-pathological Correlation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Discordance of HER2-low Status between Breast Primary and Distant Metastases with Clinical-pathological Correlation Ellen Yang, Timothy D’Alfonso, Monica Morrow, Edi Brogi, Hannah Wen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4284023/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Introduction Breast cancer with HER2 immunohistochemistry (IHC) 1+ or 2+ with negative in situ hybridization (ISH) (HER2-low) can now be targeted by HER2 antibody drug conjugates. We set out to compare HER2 status between matched primary invasive breast carcinoma (IBC) and distant metastases (DM) with clinical-pathological correlation, with specific interest in HER2-low. Methods Biomarker studies and clinical-pathological features of primary IBC with matched DM diagnosed between 2021-2022 were retrospectively analyzed. HER2 status was assessed per 2023 ASCO/CAP guidelines for IHC (Ventana, 4B5) and ISH (IQFISH pharmDX, DAKO). Bilateral breast primaries were excluded. HER2 IHC 0 to 1+ were reassessed. Results 147 cases of primary IBC with matched DM were identified (Table 1). Biomarkers were performed on core biopsy (n=74) and resection (n=73). 126 cases (86%) were initially classified as “HER2 negative”; of these 67 (46%) were reclassified as HER2-low. Patients with HER2 positive primaries were younger (p=0.01) and had an increased incidence of micropapillary carcinoma (p=0.02). HER2-low primaries also had increased incidence of micropapillary carcinoma (p=0.02) and estrogen receptor (ER) positivity (p=0.02) comparing to HER2 0. 169 matched DM cases excluding bone metastasis were identified (range of 1-7 metastases per IBC). The most common sites of metastases were liver (50/169, 30%), lung (36/169; 21%), distant lymph node (26/169, 15%). 138 DM cases (82%) were previously classified as “HER2 negative”, and 62 (37%) were reclassified as HER2-low. Like HER2-low primaries, HER2-low metastases were frequently ER positive (52/62; 84%) (p=0.02). Brain metastases were more frequently HER2 positive (5/32; 16%) (p=0.04). Comparing HER2 status in matched primaries and DM, HER2 status was discordant in 62 cases (37%). Most changes occurred from HER2-low to HER2 0 (33/169, 20 %), HER2 0 to HER2-low (17/169, 10%), and HER2-low to positive (10/169, 6%). All HER2-low to HER2 0 changes were HER2 1+ to 0. In 30 patients with multiple DM sites (47 cases), HER2 status among different DM samples was discordant in 16 patients (53%), mostly from HER2-low to HER2 0 (16/47, 34 %). Conclusion Significant proportion of previous “HER2 negative” primaries and DM cases are reclassified as HER2-low. Discordant HER2 status between IBC primary and metastasis and between different DM sites demonstrated tumor heterogeneity and highlights the need for HER2 retesting in distant metastasis. Health sciences/Oncology/Cancer/Breast cancer Health sciences/Diseases/Cancer/Tumour biomarkers Health sciences/Biomarkers/Predictive markers Health sciences/Diseases/Cancer/Metastasis Health sciences/Diseases/Cancer/Cancer therapy/Targeted therapies HER2-low HER2 0 breast carcinoma distant metastasis clinicopathological correlation Figures Figure 1 Figure 2 Figure 3 Introduction The human epidermal growth factor receptor 2 (HER2) is both a prognostic and predictive biomarker in invasive breast carcinoma, serving as a target for the monoclonal antibodies, trastuzumab and pertuzumab among other HER2-targeted compounds 1 . Fam-trastuzumab deruxtecan (T-DXd), a third generation HER2-directed antibody drug conjugate (ADC), received FDA approval for the treatment of patients with locally advanced or metastatic HER2-low breast cancer 4 . Based on a randomized trial, DB-04 demonstrated that T-DXd reduced risk of disease progression or death by 50% and increased overall survival by more than six months compared to standard chemotherapy 4 . T-DXd is composed of a monoclonal antibody (the “vehicle”) synthetically linked to a cytotoxic drug (the “payload”), that binds to the HER2 receptor on the extracellular membrane and is internalized to induce antitumor and bystander effects 2–3 . In the DB-04 trial, T-DXd showed anti- tumor effects in patients with HER2-low metastatic breast cancer, defined as HER2 IHC 1 + and IHC 2+/ISH negative 4 . Results of the DB-04 trial and the FDA approval of the HER2 ADC prompted an ASCO/CAP guideline update. The 2023 guideline update highlights the clinical relevance of HER2-low status and distinguishing HER2 IHC 0 from IHC 1 + results 1 . The guideline recommends HER2 testing in all newly diagnosed primary breast cancers, recurrences, and metastases, if tissue samples are available. Discordance in HER2 expression between primary and recurrent/metastatic breast cancers has been reported, especially in the context of HER2-low 5–8 . Interestingly, changes of HER2 status have been observed between biopsy at enrolment and subsequent biopsies when resistance to T-Dxd develops 9 . The main aim of this study was to evaluate the discordance of HER2-low status between primary breast cancer to matched distant metastases, as this will have implications for selection of specimens for HER2 IHC testing to determine eligibility for treatment. Methods This study was approved by the Institutional Review Board. The institutional database was searched to identify patients with metastatic breast cancer diagnosed at our center between 2021–2022. Only patients with HER2 testing performed in matched primary breast cancer and distant metastasis at our center were included. Clinicopathological characteristics including patient age, histologic subtype, Nottingham grade, type of surgery, neoadjuvant therapy (NAC), site of metastases, were collected. Patients with bilateral primaries were excluded. Bone metastasis specimens were excluded from this study. Biomarkers status including Estrogen Receptor (ER), Progesterone Receptor (PR), Androgen Receptor (AR), and HER2 were obtained from the pathology report. HER2 negative cases without a definitive semiquantitative score (0 to 1+) were re-reviewed by the study pathologists (EY and HYW). HER2 Assessment HER2 status was assessed per 2023 ASCO/CAP guidelines by Immunohistochemistry (IHC) and in situ hybridization (ISH) 1 . Immunohistochemistry (IHC) was performed using PATHWAY anti-HER2/neu 4B5 assay and by Roche BenchMark ULTRA ( Ventana). All HER2 IHC equivocal (2+) cases were reflexed to HER2 FISH using dual-color FISH probe (IQFISH pharmDX, DAKO) and the FISH results were classified according to the ASCO/CAP guideline 10 . Statistical analysis Statistical analysis was performed using SPSS software (v. 26; SPSS, Chicago, IL, USA) with Chi-square z-test and one-way ANOVA, and p-values of < 0.05 were considered significant. Results Patient cohort A total of 147 patients with matched primary invasive breast carcinomas and biopsy confirmed distant metastases with HER2 testing were identified. Clinicopathological features of the primary breast carcinoma are summarized in Table 1. Metastatic samples from multiple sites were available from 30 patients. Biomarkers in primary breast cancer were performed on core biopsy (n=74, 50%) or resection (n=73, 50%) specimens. Clinicopathologic characteristics of HER2-low primary breast carcinoma 126 (86%) primary breast carcinomas were classified as “HER2 negative” (0, 1+, or 2+ with negative ISH). Of these, 59 (40%) cases were HER2 0 and 67 (46%) were HER2-low, including 37 1+ cases and 30 2+ cases with negative ISH. Comparing HER2 0 vs HER2-low vs HER2 positive, there was a higher incidence of micropapillary carcinoma (0% vs 4% vs 14%, p=0.02) amongHER2 positive tumors and more prevalent ER positivity (76% vs 91% vs 67%, p=0.02) among HER2-low tumors. All metaplastic carcinomas (n=4) were HER2 0 (p=0.05). No other difference in histologic subtype, Nottingham grade, or biomarker status was identified. A comparison of available HER2 status (n=10) pre- and post- NAC in the 38 patients (26%) who received NAC and had residual tumor showed HER2 status was discordant in 50% (5/10) of the cases, including 4 cases (40%) from HER2-low to 0, and 1 case (10%) from HER2-low (IHC 2+ with negative FISH) to HER2 positive (IHC 2+ with positive FISH). HER2-low status in distant metastases 169 matched distant metastatic samples were included, representing a range of 1 to7 unique metastatic sites per primary breast carcinoma. The most common sites of metastases were liver (n=50, 30%), lung (n=36, 21%), and distant lymph node (n=26, 15%) (Table 1). 137 (82%) metastatic samples were classified as “HER2 negative”. Of these, 75 (44%) were HER2 0 and 62 (37%) were HER2-low, include 30 IHC 1+ cases and 32 IHC 2+ cases with negative FISH. Similar to HER2-low primaries, HER2-low metastases were more frequently ER positive (52/62; 84%) (p=0.02). Brain metastases were more frequently HER2 positive (5/32; 16%) (p=0.04), with no other difference in HER2 status between different sites of metastases. Discordance of HER2-low status between breast primary and distant metastases (DM) and among DM sites Comparing HER2 status in matched primaries and DM, HER2 status was discordant in 62 cases (37%) (Table 2). Most changes occurred from HER2-low to HER2 0 (33/169, 20%), HER2 0 to HER2-low (17/169, 10%), and HER2-low to positive (10/169, 6%). All HER2-low to HER2 0 changes were HER2 IHC 1+ to IHC 0. In 30 patients with multiple DM samples (47 metastatic samples, 1 to 7 metastatic samples per patient, median 2), HER2 status among DM sites was discordant in 16 patients (53%), mostly from HER2-low to HER2 0 (16/47, 34%) (Table 3). Discussion Following the emergence of new HER2-directed therapies, HER2-low breast carcinoma characterization has been the focus of many recent studies and clinical trials 4, 7–9 . Our study evaluated the discordance of HER2-low status between matched primary breast cancer and distant metastases and among different metastatic sites. In our retrospective cohort of 147 breast cancer patients with HER2 assessment in matched primary and DM, significant proportion of previous “HER2 negative” primaries (46%) and DM cases (37%) were HER2-low, similar to the reported prevalence 12 . These reclassifications have significant treatment implications. Contrary to the study reporting the enrichment of HER2-low in the metastatic cohort 13, 21 , we observed similar proportions of HER2-low tumors in the primary and distant metastases. Several factors may contribute to the discordance of HER2-low status between the primary and metastatic samples, including intra-tumoral heterogeneity, biological changes during disease progression or treatment, and pre-analytical and analytical factors. Intra-tumoral heterogeneity secondary to multiple tumor subpopulations has been reported, which may contribute to the geographical heterogeneity depending on the region sampled and explain treatment resistance 14–18 . Preanalytical issues such as cold ischemia time and tissue handling are known factors that could impact HER2 IHC and ISH 1,19 . The ASCO/CAP recommendations have specific optimal tissue handling requirements 1 . These factors are even more critical in detecting low levels of HER2 expression. Consistent with other published studies 18–19 , our study showed a statistically significant association between ER positivity and HER2-low expression. There is an increased incidence of ER positivity in both primary tumors and metastasis with HER2-low expression compared to HER2 0 cases (p = 0.02). This further supports the hypothesis of an interaction between the HER2 and hormone receptor pathways 19 . However, few studies have examined the discordance in HER2-low status between primary breast carcinoma and progressive disease 20–23 . A focus on late recurrence showed that breast cancer disease progresses with enrichment of HER2-low, with significant discordance in the HER2 expression between primary tumors and matched recurrences (37%) 20 . In our study, HER2 status was discordant in 37% of patients between matched breast primaries and DM. Previous studies hypothesized that breast cancer treatments including chemotherapy, hormone therapy and conventional anti-HER2 therapies, could modify (or even upregulate) HER2 expression levels during disease progression 24–25 . However, contrary to the enrichment of HER2-low status previously seen in recurrences 13 , the most frequent change from breast primaries to DM in our study was from HER2-low to HER2 0 (20%), followed by HER2 0 to HER2-low (10%). Interestingly, among different metastatic sites from the same breast primary, HER2 status was discordant between DM sites in 53% of patients. This observation suggests tumor heterogeneity in distant metastasis and highlights the need for HER2 retesting in distant metastasis. In DESTINY-Breast04, 35% of the samples were primary tumors and 65% were metastasis 4 . There was no significant difference in survival benefit by sample site (primary vs. metastasis) or specimen type. Currently, patients are eligible for HER2 ADC therapy if the breast cancer is HER2-low in either the primary tumor or distant metastasis. However, there is lack of data regarding whether alterations in HER2-low status during disease progression could impact the drug activity. Some limitations of our study include its single institution retrospective design. HER2 IHC was not concurrently assessed in matched breast primary and distant metastasis samples, and not all archived IHC stains were available for re-review for the study. However, at our center, we have been using anti-HER2/neu 4B5 rabbit monoclonal antibody consistently for HER2 IHC in breast cancer over the past 15 years. On slide controls with a range of HER2 protein expression were used in each HER2 IHC staining batch, and all IHC for breast cancer biomarker assessment are reviewed and reported by pathologists specialized in breast pathology, to ensure analytical standardization. In summary, in this study, we analyzed the HER2 status changes of 147 breast cancer patients between primary breast carcinoma and matched DM, with clinico-pathological correlation. HER2-low tumors comprised of a significant proportion of previous “HER2 negative” primaries and DM cases. High prevalence of discordant HER2 status between primaries and DM, and among different DM sites was identified, most frequently from HER2-low to HER2 0. This discordance demonstrates tumor heterogeneity and highlights the need for HER2 retesting in distant metastasis, especially in patients previously diagnosed as HER2 0 breast cancer. Declarations Competing interests All authors declare no financial or non-financial competing interests. Author contributions All authors contributed to this study, including conception and design (EY, TD, HW), study conduct (EY, HW), data analysis (EY) and manuscript write-up (EY, TD, MM, EB, HW). All authors read and approved the final manuscript. Acknowledgements This study received no funding. Data availability The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request. References Wolff AC, Somerfield MR, Dowsett M, et al. Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: ASCO-College of American Pathologists Guideline Update. J Clin Oncol. 2023;41(22): 3867–3872. Marchiò C, Annaratone L, Marques A, et al. Evolving concepts in HER2 evaluation in breast cancer: Heterogeneity, HER2-low carcinomas and beyond. Semin Cancer Biol. 2021;72:123–135. Ogitani Y, Hagihara K, Oitate M, et al. Bystander killing effect of DS-8201a, a novel anti-human epidermal growth factor receptor 2 antibody-drug conjugate, in tumors with human epidermal growth factor receptor 2 heterogeneity. Cancer Sci. 2016;107(7):1039–1046. Modi, S, Jacot, W, Yamashita, T, et al. DESTINY-Breast04 Trial Investigators. Trastuzumab Deruxtecan in Previously Treated HER2- Low Advanced Breast Cancer. The New England journal of medicine. 2022;387(1), 9–20. Almstedt K, Krauthauser L, Kappenberg F, et al. Discordance of HER2-Low between Primary Tumors and Matched Distant Metastases in Breast Cancer. Cancers (Basel). 2023;15(5):1413. 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Pekmezci M, Szpaderska A, Osipo C, et al. The Effect of Cold Ischemia Time and/or Formalin Fixation on Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor-2 Results in Breast Carcinoma. Patholog Res Int. 2012;2012:947041. Bergeron A, Bertaut A, Beltjens F, et al. Anticipating changes in the HER2 status of breast tumours with disease progression-towards better treatment decisions in the new era of HER2-low breast cancers. Br J Cancer. 2023;129(1):122–134. Miglietta F, Griguolo G, Bottosso M, et al. Evolution of HER2-low expression from primary to recurrent breast cancer. NPJ Breast Cancer. NPJ Breast Cancer. 2021;7(1):137. Schettini F, Chic N, Braso-Maristany F, et al. Clinical, pathological, and PAM50 gene expression features of HER2-low breast cancer. NPJ Breast Cancer. 2021;7(1):1–13. Anderson S, Bartow BB, Siegal GP, et al. The dynamics of HER2-low expression during breast cancer progression. Breast Cancer Res Treat. 2023;201(3):437–446. Dieci MV, Miglietta F, Griguolo G, et al. Biomarkers for HER2-positive metastatic breast cancer: beyond hormone receptors. Cancer Treat Rev. 2020;88:102064. Kan S, Koido S, Okamoto M, et al. Gemcitabine treatment enhances HER2 expression in low HER2-expressing breast cancer cells and enhances the antitumor effects of trastuzumab emtansine. Oncol Rep. 2015;34:504–10. Tables Table 1. HER2 status between breast primaries and distant metastasis with clinical-pathological correlation. Breast Primaries (IBC) HER2 0 (n, %) HER2-low (n, %) HER2 Positive (n, %) Total (n, %) p-value Number of patients 59 (40) 67 (46) 21 (14) 147 Clinical Median age (min, max) 53 (30-78) 52 (29-77) 46 (20-66) 51 (20-78) 0.01 Specimen for biomarker Core biopsy 27 (46) 31 (46) 16 (76) 74 (50) 0.04 Resection 32 (54) 36 (54) 5 (24) 73 (50) 0.04 Type of surgery Lumpectomy 20 (34) 19 (28) 7 (33) 46 (31) 0.78 Mastectomy 29 (49) 38 (57) 5 (24) 72(49) 0.03 N/A 10 (17) 10 (15) 9 (43) 29 (20) 0.02 Neoadjuvant treatment Number of patients 11 (19) 23 (34) 4 (19) 38 (26) 0.11 Pathologic complete response 0/11 0/23* 0/4 0/38* *1 HER2-low case had only residual LVI Histologic type IDC, NOS 42 (71) 53 (79) 16 (76) 112 (76) 0.49 ILC 8 (14) 9 (13) 1 (5) 18 (12) 0.53 Pleomorphic ILC 2 (3) 4 (6) 1 (5) 7 (5) 0.79 classic 6 (10) 5 (7) 0 11 (7) - Invasive mammary carcinoma 2 (3) 0 1 (5) 3 (2) 0.26 Invasive micropapillary carcinoma 0 3 (4) 3 (14) 6 (2) 0.02 Mucinous carcinoma 2 (3) 2 (3) 0 4 (3) 0.70 Metaplastic carcinoma 4 (7) 0 0 4 (3) 0.05 Small cell carcinoma 1 (2) 0 0 1 (1) 0.47 Nottingham grade 1 3 (5) 1 (1) 1 (5) 5 (5) 0.49 2 31 (53) 37 (55) 9 (43) 77 (52) 0.85 3 24 (41) 27 (40) 8 (38) 59 (40) 0.97 Unknown 1 (2) 2 (3) 3 (14) 6 (18) - Biomarker ER (positivity) 45 (76) 61 (91) 14 (67) 120 (82) 0.02 PR (positivity) 40 (68) 50 (50) 12 (57) 102 (69) 0.30 AR (positivity- if ER-/PR-) 5 (8) 2 (3) 1 (5) 8 (5) 0.67 Distant Metastasis (DM) HER2 0 (n, %) HER2-low (n, %) HER2 Positive (n, %) Total (n, %) p-value Number of samples 75 (44) 62 (37) 32(19) 169 Site of metastasis Liver 24 (32) 19 (31) 7 (22) 50 (30) 0.51 Lung 14 (19) 16 (26) 6 (19) 36 (21) 0.53 Lymph node (distant) 8 (11) 9 (15) 9 (28) 26 (15) 0.09 Soft tissue 9 (12) 2 (3) 4 (13) 15 (9) 0.15 Pleura/Pleural fluid 9 (12) 5 (8) 2 (6) 16 (9) 0.56 Skin 4 (5) 7 (11) 0 11 (7) 0.09 Brain 2 (3) 3 (5) 5 (16) 10 (6) 0.04 Gastrointestinal 3 (4) 1 (2) 0 4 (2) 0.40 Peritoneal fluid 2 (3) 1 (2) 0 3 (2) 0.62 Retroperitoneum 0 1 (2) 0 1 (1) 0.42 Thyroid 1 (1) 0 0 1 (1) 0.53 Adrenal 1 (1) 0 0 1 (1) 0.53 Pericardial fluid 0 1 (2) 0 1 (1) 0.42 Biomarker ER (positivity) 53 (71) 52 (84) 17 (53) 122 (72) 0.002 PR (positivity) 27 (36) 22 (35) 7 (22) 56 (33) 0.27 AR (positivity- if ER-/PR-) 6 (8) 7 (11) 3 (9) 16 (9) 0.73 Table 2: Discordance of HER2 expression from primary to distant metastatic breast carcinoma. Distant Metastasis (DM) HER2 0 (n, %) HER2-low (n, %) HER2 Positive (n, %) Total (n, %) HER2 0 primary 41 (24) 17 (10) 0 58 (34) HER2-low primary 33 (20) 44 (26) 10 (6) 87 (51) HER2 Positive primary 1 (1) 1 (1) 22 (13) 24 (14) Total 75 (44) 62 (37) 32 (19) 169 Table 3: Discordance of HER2 expression between distant metastatic sites of breast carcinoma (range=1-7 metastatic sites). Distant Metastatic (DM) sites 2-7 HER2 0 (n, %) HER2-low (n, %) HER2 Positive (n, %) Total (n, %) HER2 Neg Met site 1 6 (13) 1 (2) 1 (2) 8 (17) HER2-low Met site 1 16 (34) 13 (28) 1 (2) 30 (64) HER2 Pos Met site 1 0 1 (2) 8 (17) 9 (19) Total 22 (47) 15 (32) 10 (21) 47 Additional Declarations (Not answered) Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4284023","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":295429109,"identity":"0d8b7744-0e43-4556-99ee-f5492f8df7b4","order_by":0,"name":"Ellen Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwklEQVRIiWNgGAWjYNACAxsGBh7StBSkkazlw2EStBgcP3v4xQeD89HyPYcffmCouGfXQFDLmbw0yxkGt3M3nG0zlmA4U5xMWMuBHDNjHpAWfh42Bsa2hGTCDjv/xsz4j8G53Pn9RGu5kWP8GGhXbsPZHrAWO4JaJG+8MWPsMUjO3XDmmLFEwpmEBIJa+M7nGH/48ccud35P8sMPHyoS7AlqUTjAwCYB5wGtSGwgpEW+gYH5A7IAYVtGwSgYBaNgxAEAlutA3YG1D4IAAAAASUVORK5CYII=","orcid":"https://orcid.org/0009-0008-9557-5988","institution":"Memorial Sloan Kettering Cancer Center","correspondingAuthor":true,"prefix":"","firstName":"Ellen","middleName":"","lastName":"Yang","suffix":""},{"id":295429110,"identity":"52911f9c-e03b-4169-8d48-056bc4cebec3","order_by":1,"name":"Timothy D’Alfonso","email":"","orcid":"","institution":"Northwell Health","correspondingAuthor":false,"prefix":"","firstName":"Timothy","middleName":"","lastName":"D’Alfonso","suffix":""},{"id":295429111,"identity":"a416383f-7bb9-4c7b-bc55-82d7d83dfcac","order_by":2,"name":"Monica Morrow","email":"","orcid":"","institution":"Memorial Sloan Kettering Cancer Center","correspondingAuthor":false,"prefix":"","firstName":"Monica","middleName":"","lastName":"Morrow","suffix":""},{"id":295429112,"identity":"110a3567-6546-4fd3-a1e1-b75090b734ef","order_by":3,"name":"Edi Brogi","email":"","orcid":"https://orcid.org/0000-0003-4737-8468","institution":"Memorial Sloan Kettering Cancer Center","correspondingAuthor":false,"prefix":"","firstName":"Edi","middleName":"","lastName":"Brogi","suffix":""},{"id":295429113,"identity":"b712e179-220d-42f6-9c52-f03659e8a518","order_by":4,"name":"Hannah Wen","email":"","orcid":"","institution":"Memorial Sloan Kettering Cancer Center","correspondingAuthor":false,"prefix":"","firstName":"Hannah","middleName":"","lastName":"Wen","suffix":""}],"badges":[],"createdAt":"2024-04-17 21:25:19","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4284023/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4284023/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":55765159,"identity":"75f9751f-e8dd-4ec4-aea3-30011376e9dc","added_by":"auto","created_at":"2024-05-02 20:06:28","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":359550,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDiscordance of HER2 expression from primary to distant metastatic breast carcinoma\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4284023/v1/0e9e4b1e7e22a97bbc2f951d.jpg"},{"id":55765162,"identity":"26eb190d-37a0-45dc-83d7-fe6c7cb1e34c","added_by":"auto","created_at":"2024-05-02 20:06:28","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3205234,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDiscordant HER2 status between primary to distant metastatic breast carcinoma. \u003c/strong\u003eTop 2 panels: HER2-low (IHC 1+) (A, B: IBC, 2018) to HER2 0 (C,D: liver, 2022). Bottom 2 panels: HER2 0 (E, F: IBC, 2018) to HER2-low (IHC 2+/ISH-); G, H: mediastinal LN, 2020) (A, C, E, G: H\u0026amp;E; B, D, F, H: HER2 IHC).\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4284023/v1/47e687ed17859314bdd4fa98.jpg"},{"id":55765160,"identity":"085bc8c2-9304-48d0-8908-4ee9997bd5b0","added_by":"auto","created_at":"2024-05-02 20:06:28","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2726809,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDiscordant HER2 status between distant metastatic sites of breast carcinoma. \u003c/strong\u003eTop 3 panels: Temporal heterogeneity: HER2-low (2+/-ISH) (A,B: liver, 2020) to HER2 0 (C, D: liver, 2021) to HER2-low (2+/-ISH) (E, F: liver, 2022). Bottom 2 panels: Spatial heterogeneity: HER2-low (IHC 1+) (G,H: liver, 2022) to HER2 positive (2+/+ISH) (I,J: lung, 2023). (A, C, E, G, I : H\u0026amp;E; B, D, F, H, J: HER2 IHC).\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4284023/v1/c4026fa4dca0401a2b49b596.jpg"},{"id":56221330,"identity":"67069b21-4668-4fc9-b1f5-bed4238014c1","added_by":"auto","created_at":"2024-05-10 04:38:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1352704,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4284023/v1/31680f40-2269-45dc-afbb-54353a7cbbb0.pdf"}],"financialInterests":"(Not answered)","formattedTitle":"Discordance of HER2-low Status between Breast Primary and Distant Metastases with Clinical-pathological Correlation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe human epidermal growth factor receptor 2 (HER2) is both a prognostic and predictive biomarker in invasive breast carcinoma, serving as a target for the monoclonal antibodies, trastuzumab and pertuzumab among other HER2-targeted compounds\u003csup\u003e1\u003c/sup\u003e. Fam-trastuzumab deruxtecan (T-DXd), a third generation HER2-directed antibody drug conjugate (ADC), received FDA approval for the treatment of patients with locally advanced or metastatic HER2-low breast cancer\u003csup\u003e4\u003c/sup\u003e. Based on a randomized trial, DB-04 demonstrated that T-DXd reduced risk of disease progression or death by 50% and increased overall survival by more than six months compared to standard chemotherapy\u003csup\u003e4\u003c/sup\u003e. T-DXd is composed of a monoclonal antibody (the \u0026ldquo;vehicle\u0026rdquo;) synthetically linked to a cytotoxic drug (the \u0026ldquo;payload\u0026rdquo;), that binds to the HER2 receptor on the extracellular membrane and is internalized to induce antitumor and bystander effects\u003csup\u003e2\u0026ndash;3\u003c/sup\u003e. In the DB-04 trial, T-DXd showed anti- tumor effects in patients with HER2-low metastatic breast cancer, defined as HER2 IHC 1\u0026thinsp;+\u0026thinsp;and IHC 2+/ISH negative\u003csup\u003e4\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e Results of the DB-04 trial and the FDA approval of the HER2 ADC prompted an ASCO/CAP guideline update. The 2023 guideline update highlights the clinical relevance of HER2-low status and distinguishing HER2 IHC 0 from IHC 1\u0026thinsp;+\u0026thinsp;results\u003csup\u003e1\u003c/sup\u003e. The guideline recommends HER2 testing in all newly diagnosed primary breast cancers, recurrences, and metastases, if tissue samples are available. Discordance in HER2 expression between primary and recurrent/metastatic breast cancers has been reported, especially in the context of HER2-low\u003csup\u003e5\u0026ndash;8\u003c/sup\u003e. Interestingly, changes of HER2 status have been observed between biopsy at enrolment and subsequent biopsies when resistance to T-Dxd develops\u003csup\u003e9\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe main aim of this study was to evaluate the discordance of HER2-low status between primary breast cancer to matched distant metastases, as this will have implications for selection of specimens for HER2 IHC testing to determine eligibility for treatment.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e This study was approved by the Institutional Review Board. The institutional database was searched to identify patients with metastatic breast cancer diagnosed at our center between 2021\u0026ndash;2022. Only patients with HER2 testing performed in matched primary breast cancer and distant metastasis at our center were included. Clinicopathological characteristics including patient age, histologic subtype, Nottingham grade, type of surgery, neoadjuvant therapy (NAC), site of metastases, were collected. Patients with bilateral primaries were excluded. Bone metastasis specimens were excluded from this study. Biomarkers status including Estrogen Receptor (ER), Progesterone Receptor (PR), Androgen Receptor (AR), and HER2 were obtained from the pathology report. HER2 negative cases without a definitive semiquantitative score (0 to 1+) were re-reviewed by the study pathologists (EY and HYW).\u003c/p\u003e \u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eHER2 Assessment\u003c/span\u003e \u003c/p\u003e \u003cp\u003eHER2 status was assessed per 2023 ASCO/CAP guidelines by Immunohistochemistry (IHC) and in situ hybridization (ISH)\u003csup\u003e1\u003c/sup\u003e. Immunohistochemistry (IHC) was performed using PATHWAY anti-HER2/neu 4B5 assay and by Roche BenchMark ULTRA \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003e(\u003c/span\u003eVentana). All HER2 IHC equivocal (2+) cases were reflexed to HER2 FISH using dual-color FISH probe (IQFISH pharmDX, DAKO) and the FISH results were classified according to the ASCO/CAP guideline\u003csup\u003e10\u003c/sup\u003e.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eStatistical analysis was performed using SPSS software (v. 26; SPSS, Chicago, IL, USA) with Chi-square z-test and one-way ANOVA, and p-values of \u0026lt;\u0026thinsp;0.05 were considered significant.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cu\u003ePatient cohort\u0026nbsp;\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eA total of 147 patients with matched primary invasive breast carcinomas and biopsy confirmed distant metastases with HER2 testing were identified. Clinicopathological features of the primary breast carcinoma are summarized in Table 1. Metastatic samples from multiple sites were available from 30 patients. Biomarkers in primary breast cancer were performed on core biopsy (n=74, 50%) or resection (n=73, 50%) specimens.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eClinicopathologic characteristics of HER2-low primary breast carcinoma\u0026nbsp;\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003e126 (86%) primary breast carcinomas were classified as “HER2 negative” (0, 1+, or 2+ with negative ISH). Of these, 59 (40%) cases were HER2 0 and 67 (46%) were HER2-low, including 37 1+ cases and 30 2+ cases with negative ISH. \u0026nbsp;Comparing HER2 0 vs HER2-low vs HER2 positive, there was a higher incidence of micropapillary carcinoma (0% vs 4% vs 14%, p=0.02) amongHER2 positive tumors and more prevalent ER positivity (76% vs 91% vs 67%, p=0.02) among HER2-low tumors. All metaplastic carcinomas (n=4) were HER2 0 (p=0.05). No other difference in histologic subtype, Nottingham grade, or biomarker status was identified.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eA comparison of available HER2 status (n=10) pre- and post- NAC in the 38 patients (26%) who received NAC and had residual tumor showed HER2 status was discordant in 50% (5/10) of the cases, including 4 cases (40%) from HER2-low to 0, and 1 case (10%) from HER2-low (IHC 2+ with negative FISH) to HER2 positive (IHC 2+ with positive FISH).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eHER2-low status in distant metastases\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003e169 matched distant metastatic samples were included, representing a range of 1 to7 unique metastatic sites per primary breast carcinoma. The most common sites of metastases were liver (n=50, 30%), lung (n=36, 21%), and distant lymph node (n=26, 15%) (Table 1). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e137 (82%) metastatic samples were classified as\u0026nbsp;“HER2 negative”. Of these, 75 (44%) were HER2 0 and 62 (37%) were HER2-low, include 30 IHC 1+ cases and 32 IHC 2+ cases with negative FISH. Similar to HER2-low primaries, HER2-low metastases were more frequently ER positive (52/62; 84%) (p=0.02). Brain metastases were more frequently HER2 positive (5/32; 16%) (p=0.04), with no other difference in HER2 status between different sites of metastases.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eDiscordance of HER2-low status between breast primary and distant metastases (DM) and among DM sites\u003c/u\u003e\u003c/p\u003e\n\u003cp\u003eComparing HER2 status in matched primaries and DM, HER2 status was discordant in 62 cases (37%) (Table 2). Most changes occurred from HER2-low to HER2 0 (33/169, 20%), HER2 0 to HER2-low (17/169, 10%), and HER2-low to positive (10/169, 6%). All HER2-low to HER2 0 changes were HER2 IHC 1+ to IHC 0.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn 30 patients with multiple DM samples (47 metastatic samples, 1 to 7 metastatic samples per patient, median 2), HER2 status among DM sites was discordant in 16 patients (53%), mostly from HER2-low to HER2 0 (16/47, 34%) (Table 3).\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eFollowing the emergence of new HER2-directed therapies, HER2-low breast carcinoma characterization has been the focus of many recent studies and clinical trials \u003csup\u003e4, 7\u0026ndash;9\u003c/sup\u003e. Our study evaluated the discordance of HER2-low status between matched primary breast cancer and distant metastases and among different metastatic sites.\u003c/p\u003e \u003cp\u003eIn our retrospective cohort of 147 breast cancer patients with HER2 assessment in matched primary and DM, significant proportion of previous \u0026ldquo;HER2 negative\u0026rdquo; primaries (46%) and DM cases (37%) were HER2-low, similar to the reported prevalence\u003csup\u003e12\u003c/sup\u003e. These reclassifications have significant treatment implications. Contrary to the study reporting the enrichment of HER2-low in the metastatic cohort\u003csup\u003e13, 21\u003c/sup\u003e, we observed similar proportions of HER2-low tumors in the primary and distant metastases.\u003c/p\u003e \u003cp\u003eSeveral factors may contribute to the discordance of HER2-low status between the primary and metastatic samples, including intra-tumoral heterogeneity, biological changes during disease progression or treatment, and pre-analytical and analytical factors. Intra-tumoral heterogeneity secondary to multiple tumor subpopulations has been reported, which may contribute to the geographical heterogeneity depending on the region sampled and explain treatment resistance\u003csup\u003e14\u0026ndash;18\u003c/sup\u003e. Preanalytical issues such as cold ischemia time and tissue handling are known factors that could impact HER2 IHC and ISH\u003csup\u003e1,19\u003c/sup\u003e. The ASCO/CAP recommendations have specific optimal tissue handling requirements\u003csup\u003e1\u003c/sup\u003e. These factors are even more critical in detecting low levels of HER2 expression.\u003c/p\u003e \u003cp\u003eConsistent with other published studies\u003csup\u003e18\u0026ndash;19\u003c/sup\u003e, our study showed a statistically significant association between ER positivity and HER2-low expression. There is an increased incidence of ER positivity in both primary tumors and metastasis with HER2-low expression compared to HER2 0 cases (p\u0026thinsp;=\u0026thinsp;0.02). This further supports the hypothesis of an interaction between the HER2 and hormone receptor pathways\u003csup\u003e19\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, few studies have examined the discordance in HER2-low status between primary breast carcinoma and progressive disease\u003csup\u003e20\u0026ndash;23\u003c/sup\u003e. A focus on late recurrence showed that breast cancer disease progresses with enrichment of HER2-low, with significant discordance in the HER2 expression between primary tumors and matched recurrences (37%)\u003csup\u003e20\u003c/sup\u003e. In our study, HER2 status was discordant in 37% of patients between matched breast primaries and DM. Previous studies hypothesized that breast cancer treatments including chemotherapy, hormone therapy and conventional anti-HER2 therapies, could modify (or even upregulate) HER2 expression levels during disease progression\u003csup\u003e24\u0026ndash;25\u003c/sup\u003e. However, contrary to the enrichment of HER2-low status previously seen in recurrences\u003csup\u003e13\u003c/sup\u003e, the most frequent change from breast primaries to DM in our study was from HER2-low to HER2 0 (20%), followed by HER2 0 to HER2-low (10%). Interestingly, among different metastatic sites from the same breast primary, HER2 status was discordant between DM sites in 53% of patients. This observation suggests tumor heterogeneity in distant metastasis and highlights the need for HER2 retesting in distant metastasis. In DESTINY-Breast04, 35% of the samples were primary tumors and 65% were metastasis\u003csup\u003e4\u003c/sup\u003e. There was no significant difference in survival benefit by sample site (primary vs. metastasis) or specimen type. Currently, patients are eligible for HER2 ADC therapy if the breast cancer is HER2-low in either the primary tumor or distant metastasis. However, there is lack of data regarding whether alterations in HER2-low status during disease progression could impact the drug activity.\u003c/p\u003e \u003cp\u003eSome limitations of our study include its single institution retrospective design. HER2 IHC was not concurrently assessed in matched breast primary and distant metastasis samples, and not all archived IHC stains were available for re-review for the study. However, at our center, we have been using anti-HER2/neu 4B5 rabbit monoclonal antibody consistently for HER2 IHC in breast cancer over the past 15 years. On slide controls with a range of HER2 protein expression were used in each HER2 IHC staining batch, and all IHC for breast cancer biomarker assessment are reviewed and reported by pathologists specialized in breast pathology, to ensure analytical standardization.\u003c/p\u003e \u003cp\u003eIn summary, in this study, we analyzed the HER2 status changes of 147 breast cancer patients between primary breast carcinoma and matched DM, with clinico-pathological correlation. HER2-low tumors comprised of a significant proportion of previous \u0026ldquo;HER2 negative\u0026rdquo; primaries and DM cases. High prevalence of discordant HER2 status between primaries and DM, and among different DM sites was identified, most frequently from HER2-low to HER2 0. This discordance demonstrates tumor heterogeneity and highlights the need for HER2 retesting in distant metastasis, especially in patients previously diagnosed as HER2 0 breast cancer.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eAll authors declare no financial or non-financial competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor contributions\u003c/h2\u003e \u003cp\u003eAll authors contributed to this study, including conception and design (EY, TD, HW), study conduct (EY, HW), data analysis (EY) and manuscript write-up (EY, TD, MM, EB, HW). All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThis study received no funding.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eThe datasets used and/or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWolff AC, Somerfield MR, Dowsett M, et al. Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: ASCO-College of American Pathologists Guideline Update. J Clin Oncol. 2023;41(22): 3867\u0026ndash;3872.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMarchi\u0026ograve; C, Annaratone L, Marques A, et al. Evolving concepts in HER2 evaluation in breast cancer: Heterogeneity, HER2-low carcinomas and beyond. Semin Cancer Biol. 2021;72:123\u0026ndash;135.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOgitani Y, Hagihara K, Oitate M, et al. Bystander killing effect of DS-8201a, a novel anti-human epidermal growth factor receptor 2 antibody-drug conjugate, in tumors with human epidermal growth factor receptor 2 heterogeneity. Cancer Sci. 2016;107(7):1039\u0026ndash;1046.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eModi, S, Jacot, W, Yamashita, T, et al. DESTINY-Breast04 Trial Investigators. Trastuzumab Deruxtecan in Previously Treated HER2- Low Advanced Breast Cancer. The New England journal of medicine. 2022;387(1), 9\u0026ndash;20.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAlmstedt K, Krauthauser L, Kappenberg F, et al. Discordance of HER2-Low between Primary Tumors and Matched Distant Metastases in Breast Cancer. Cancers (Basel). 2023;15(5):1413.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGrassini D, Cascardi E, Sarotto I, et al. Unusual Patterns of HER2 Expression in Breast Cancer: Insights and Perspectives. Pathobiology. 2022;89:278\u0026ndash;296.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eModi S, Saura C, Yamashita T, et al. Trastuzumab Deruxtecan in Previously Treated HER2-Positive Breast Cancer. N Engl J Med. 2020;382(7):610\u0026ndash;621.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndr\u0026eacute; F, Hee Park Y, Kim SB, et al. Trastuzumab deruxtecan versus treatment of physician's choice in patients with HER2-positive metastatic breast cancer (DESTINY-Breast02): a randomised, open-label, multicentre, phase 3 trial. Lancet. 2023;401(10390):1773\u0026ndash;1785.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMosele F, Deluche E, Lusque A, et al. Trastuzumab deruxtecan in metastatic breast cancer with variable HER2 expression: the phase 2 DAISY trial. Nat Med. 2023;29(8):2110\u0026ndash;2120.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWolff AC, Hammond MEH, Allison KH, et al. Human Epidermal Growth Factor Receptor 2 Testing in Breast Cancer: American Society of Clinical Oncology/College of American Pathologists Clinical Practice Guideline Focused Update. J Clin Oncol. 2018;36(20):2105\u0026ndash;2122.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKrishnamurti, U, Fitzgibbons, P, Connolly, J, et al. Protocol for the Examination of Resection Specimens from Patients with Invasive Carcinoma of the Breast. CAP Cancer Reporting and Biomarker Reporting Protocols. CAP Cancer and CAP Pathology Electronic Reporting Committees2023.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchalper KA, Kumar S, Hui P, et al. A retrospective population-based comparison of HER2 immunohistochemistry and fluorescence in situ hybridization in breast carcinomas: impact of 2007 American Society of Clinical Oncology/College of American Pathologists criteria. Arch Pathol Lab Med. 2014;138: 213\u0026ndash;219.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVan Poznak C, Somerfield M, Bast, R. et al. Use of biomarkers to guide decisions on systemic therapy for women with metastatic breast cancer: American society of clinical oncology clinical practice guideline. J Clin Oncol. 2015; 33: 2695\u0026ndash;2704.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFilho OM, Viale G, Stein S, et al. Impact of HER2 heterogeneity on treatment response of early-stage HER2-positive breast cancer: phase II Neoadjuvant Clinical Trial of T-DM1 combined with pertuzumab. Cancer Discov. 2021;11:2474\u0026ndash;87.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGianni L, Pienkowski T, Im YH, et al. Efficacy and safety of neoadjuvant pertuzumab and trastuzumab in women with locally advanced, inflammatory, or early HER2-positive breast cancer (NeoSphere): a randomised multicentre, open-label, phase 2 trial. Lancet Oncol. 2012;13:25\u0026ndash;32.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaselga J, Bradbury I, Eidtmann H, et al. Lapatinib with trastuzumab for HER2-positive early breast cancer (NeoALTTO): a randomised, open-label, multicentre, phase 3 trial. Lancet. 2012;379:633\u0026ndash;40.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eViale G, Munzone E. Treatment selection for patients with equivocal HER2 status and in luminal versus HER2-enriched disease. Breast. 2019;48:S49\u0026ndash;52.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFernandez AI, Liu M, Bellizzi A, et al. Examination of low ERBB2 protein expression in breast cancer tissue. JAMA Oncol. 2022;8:607\u0026ndash;610.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePekmezci M, Szpaderska A, Osipo C, et al. The Effect of Cold Ischemia Time and/or Formalin Fixation on Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor-2 Results in Breast Carcinoma. Patholog Res Int. 2012;2012:947041.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBergeron A, Bertaut A, Beltjens F, et al. Anticipating changes in the HER2 status of breast tumours with disease progression-towards better treatment decisions in the new era of HER2-low breast cancers. Br J Cancer. 2023;129(1):122\u0026ndash;134.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiglietta F, Griguolo G, Bottosso M, et al. Evolution of HER2-low expression from primary to recurrent breast cancer. NPJ Breast Cancer. NPJ Breast Cancer. 2021;7(1):137.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchettini F, Chic N, Braso-Maristany F, et al. Clinical, pathological, and PAM50 gene expression features of HER2-low breast cancer. NPJ Breast Cancer. 2021;7(1):1\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAnderson S, Bartow BB, Siegal GP, et al. The dynamics of HER2-low expression during breast cancer progression. Breast Cancer Res Treat. 2023;201(3):437\u0026ndash;446.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDieci MV, Miglietta F, Griguolo G, et al. Biomarkers for HER2-positive metastatic breast cancer: beyond hormone receptors. Cancer Treat Rev. 2020;88:102064.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKan S, Koido S, Okamoto M, et al. Gemcitabine treatment enhances HER2 expression in low HER2-expressing breast cancer cells and enhances the antitumor effects of trastuzumab emtansine. Oncol Rep. 2015;34:504\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1. HER2 status between breast primaries and distant metastasis with clinical-pathological correlation.\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"572\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eBreast Primaries (IBC)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 0\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2-low (n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 Positive\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003ep-value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eNumber of patients\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e59 (40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e67 (46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e21 (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eClinical \u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eMedian age (min, max)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e53\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(30-78)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e52\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(29-77)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e46\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(20-66)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e51\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e(20-78)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.01\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eSpecimen for biomarker\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eCore biopsy\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e27 (46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e31 (46)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e16 (76)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e74 (50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.04\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eResection\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e32 (54)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e36 (54)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e5 (24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e73 (50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.04\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eType of surgery\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eLumpectomy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e20 (34)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e19 (28)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (33)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e46 (31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eMastectomy\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e29 (49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e38 (57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e5 (24)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e72(49)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.03\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eN/A\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e10 (17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e10 (15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e9 (43)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e29 (20)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.02\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eNeoadjuvant treatment\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eNumber of patients\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e11 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e23 (34)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e38 (26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" rowspan=\"2\" valign=\"bottom\"\u003e\n \u003cp\u003ePathologic complete response\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0/11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0/23*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0/4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e0/38*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"5\" valign=\"bottom\"\u003e\n \u003cp\u003e*1 HER2-low case had only residual LVI\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHistologic type\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eIDC, NOS\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e42 (71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e53 (79)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e16 (76)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e112 (76)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eILC\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e18 (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePleomorphic ILC\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.79\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eclassic\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (10)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e5 (7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e11 (7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eInvasive mammary carcinoma\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eInvasive micropapillary carcinoma\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 (4)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e3 (14)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.02\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eMucinous carcinoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eMetaplastic carcinoma\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e4 (7)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.05\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eSmall cell carcinoma\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eNottingham grade\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e5 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e31 (53)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e37 (55)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (43)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e77 (52)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e24 (41)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e27 (40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (38)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e59 (40)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eUnknown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (18)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eBiomarker\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eER (positivity)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e45 (76)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e61 (91)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e14 (67)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e120 (82)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.02\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePR (positivity)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e40 (68)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e50 (50)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e12 (57)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e102 (69)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eAR (positivity- if ER-/PR-)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e5 (8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eDistant Metastasis (DM)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 0\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2-low\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 Positive\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003ep-value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eNumber of samples\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e75 (44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e62 (37)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e32(19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e169\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eSite of metastasis\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eLiver\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e24 (32)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e19 (31)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (22)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e50 (30)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.51\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eLung\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e14 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e16 (26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e36 (21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eLymph node (distant)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (28)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e26 (15)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eSoft tissue\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e15 (9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePleura/Pleural fluid\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (12)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e5 (8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e16 (9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eSkin\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e11 (7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eBrain\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e5 (16)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e10 (6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.04\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eGastrointestinal\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e4 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePeritoneal fluid\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e2 (3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eRetroperitoneum\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eThyroid\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eAdrenal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePericardial fluid\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"100%\" colspan=\"6\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eBiomarker\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eER (positivity)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e53 (71)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e52 (84)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e17 (53)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e122 (72)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.002\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003ePR (positivity)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e27 (36)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e22 (35)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (22)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e56 (33)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"32.399299474605954%\" valign=\"bottom\"\u003e\n \u003cp\u003eAR (positivity- if ER-/PR-)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.660245183887916%\" valign=\"bottom\"\u003e\n \u003cp\u003e7 (11)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"11.908931698774081%\" valign=\"bottom\"\u003e\n \u003cp\u003e3 (9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"16.46234676007005%\" valign=\"bottom\"\u003e\n \u003cp\u003e16 (9)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"12.784588441330998%\" valign=\"bottom\"\u003e\n \u003cp\u003e0.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2: Discordance of HER2 expression from primary to distant metastatic breast carcinoma.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"499\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eDistant Metastasis (DM)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 0\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2-low\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 Positive\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2 0 primary\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e41 (24)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e17 (10)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e58 (34)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2-low primary\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e33 (20)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e44 (26)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e10 (6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e87 (51)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2 Positive primary\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e22 (13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e24 (14)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e75 (44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e62 (37)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e32 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e169\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 3: Discordance of HER2 expression between distant metastatic sites of breast carcinoma (range=1-7 metastatic sites).\u0026nbsp;\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"499\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eDistant Metastatic (DM) sites 2-7\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 0\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2-low\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eHER2 Positive\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(n, %)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2 Neg Met site 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e6 (13)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (17)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2-low Met site 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cstrong\u003e16 (34)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e13 (28)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e30 (64)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eHER2 Pos Met site 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e1 (2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e8 (17)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e9 (19)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"37.14859437751004%\" valign=\"bottom\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"14.65863453815261%\" valign=\"bottom\"\u003e\n \u003cp\u003e22 (47)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"15.662650602409638%\" valign=\"bottom\"\u003e\n \u003cp\u003e15 (32)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"13.654618473895582%\" valign=\"bottom\"\u003e\n \u003cp\u003e10 (21)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"18.87550200803213%\" valign=\"bottom\"\u003e\n \u003cp\u003e47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"HER2-low, HER2 0, breast carcinoma, distant metastasis, clinicopathological correlation ","lastPublishedDoi":"10.21203/rs.3.rs-4284023/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4284023/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Introduction\r\nBreast cancer with HER2 immunohistochemistry (IHC) 1+ or 2+ with negative in situ hybridization (ISH) (HER2-low) can now be targeted by HER2 antibody drug conjugates. We set out to compare HER2 status between matched primary invasive breast carcinoma (IBC) and distant metastases (DM) with clinical-pathological correlation, with specific interest in HER2-low. \r\n\r\nMethods \r\nBiomarker studies and clinical-pathological features of primary IBC with matched DM diagnosed between 2021-2022 were retrospectively analyzed. HER2 status was assessed per 2023 ASCO/CAP guidelines for IHC (Ventana, 4B5) and ISH (IQFISH pharmDX, DAKO). Bilateral breast primaries were excluded. HER2 IHC 0 to 1+ were reassessed. \r\n\r\nResults \r\n147 cases of primary IBC with matched DM were identified (Table 1). Biomarkers were performed on core biopsy (n=74) and resection (n=73). 126 cases (86%) were initially classified as “HER2 negative”; of these 67 (46%) were reclassified as HER2-low. Patients with HER2 positive primaries were younger (p=0.01) and had an increased incidence of micropapillary carcinoma (p=0.02). HER2-low primaries also had increased incidence of micropapillary carcinoma (p=0.02) and estrogen receptor (ER) positivity (p=0.02) comparing to HER2 0. 169 matched DM cases excluding bone metastasis were identified (range of 1-7 metastases per IBC). The most common sites of metastases were liver (50/169, 30%), lung (36/169; 21%), distant lymph node (26/169, 15%). 138 DM cases (82%) were previously classified as “HER2 negative”, and 62 (37%) were reclassified as HER2-low. Like HER2-low primaries, HER2-low metastases were frequently ER positive (52/62; 84%) (p=0.02). Brain metastases were more frequently HER2 positive (5/32; 16%) (p=0.04). Comparing HER2 status in matched primaries and DM, HER2 status was discordant in 62 cases (37%). Most changes occurred from HER2-low to HER2 0 (33/169, 20 %), HER2 0 to HER2-low (17/169, 10%), and HER2-low to positive (10/169, 6%). All HER2-low to HER2 0 changes were HER2 1+ to 0. In 30 patients with multiple DM sites (47 cases), HER2 status among different DM samples was discordant in 16 patients (53%), mostly from HER2-low to HER2 0 (16/47, 34 %). \r\n\r\nConclusion \r\nSignificant proportion of previous “HER2 negative” primaries and DM cases are reclassified as HER2-low. Discordant HER2 status between IBC primary and metastasis and between different DM sites demonstrated tumor heterogeneity and highlights the need for HER2 retesting in distant metastasis.","manuscriptTitle":"Discordance of HER2-low Status between Breast Primary and Distant Metastases with Clinical-pathological Correlation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-02 20:06:23","doi":"10.21203/rs.3.rs-4284023/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1aab5547-29ad-4e85-a10e-e13b457c7562","owner":[],"postedDate":"May 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":31153904,"name":"Health sciences/Oncology/Cancer/Breast cancer"},{"id":31153905,"name":"Health sciences/Diseases/Cancer/Tumour biomarkers"},{"id":31153906,"name":"Health sciences/Biomarkers/Predictive markers"},{"id":31153907,"name":"Health sciences/Diseases/Cancer/Metastasis"},{"id":31153908,"name":"Health sciences/Diseases/Cancer/Cancer therapy/Targeted therapies"}],"tags":[],"updatedAt":"2024-05-10T04:30:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-02 20:06:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4284023","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4284023","identity":"rs-4284023","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}