Comparative immunohistochemical expression of TROP2 in brain metastatic and primary tumors

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This study evaluates TROP2 expression in brain metastases from diverse solid tumors and its consistency with primary tumors, addressing the limited research on TROP2 heterogeneity and its implications for CNS-targeted therapies. Methods TROP2 immunohistochemical staining was performed on 61 brain metastatic tumors and 14 corresponding primary tumors. Based on TROP2 expression, cases were categorized into three groups: diffuse positive (> 95%), focal positive (0–95%), and negative (0%). Results Among the 61 brain metastatic tumors, TROP2 expression was diffusely positive in 62.3%, focally positive in 16.4%, and negative in 21.3%. Diffuse TROP2 positivity was most observed in tumors of lung origin, while focal positivity was predominant in colorectal metastases. In terms of pathologic diagnosis, adenocarcinoma was the most common type, with 55.6% showing diffuse positivity, 33.3% showing focal positivity, and 11.1% showing negativity. Notably, all cases of invasive breast carcinoma of no special type (IBC-NST) exhibited diffuse TROP2 positivity. No significant association was found between TROP2 expression levels and post-CNS metastasis survival. In the paired analysis of 14 cases with both primary and metastatic tumors, TROP2 expression was consistent between primary and metastatic sites in 78.6% of cases. However, 21.4% of cases, including colorectal adenocarcinoma and kidney clear cell carcinoma, showed discordant expression patterns between the primary and metastatic lesions. Conclusion This study demonstrated variable TROP2 expression in brain metastasis samples and confirmed high consistency of TROP2 expression between primary and brain metastatic lesions. TROP2 Brain metastasis Immunohistochemistry Cancer Primary tumor Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction The human trophoblast cell surface antigen 2 (TROP2) is a transmembrane glycoprotein that acts as an intracellular calcium signal transducer, driving self-renewal, cell proliferation, invasion, and survival [ 1 , 2 ]. It is overexpressed in various solid tumors, including breast [ 3 ], Colorectal [ 4 , 5 ], lung [ 6 ], gastric [ 7 ], skin [ 8 ], and pancreatic cancers [ 9 ], with expression reported in 55–75% of cases. Overexpression of TROP2 is generally associated to poor prognosis, increased tumor aggressiveness, and higher metastatic potential [ 10 , 11 ]. Metastatic solid tumors remain a significant unmet medical challenge, particularly central nervous system (CNS) metastases, which are associated with extremely poor outcomes. While targeted therapies, such as monoclonal antibodies and antibody-drug conjugates (ADCs), have improved outcomes in advanced cancer, their efficacy against CNS metastases is limited. Sacituzumab govitecan (SG), a TROP2-directed ADC, has demonstrated significant overall survival (OS) benefits in patients with triple-negative breast cancer (TNBC) [ 12 ] but showed no OS improvement for those with CNS metastases [ 13 ]. The prevailing explanation attributes this limitation to the inability of these therapies to effectively penetrate the blood-brain barrier (BBB) [ 14 ]. However, the distinct molecular and genomic features of CNS metastases, which often diverge from those of the primary tumor, must also be considered [ 15 ]. Research on TROP2 heterogeneity between primary and metastatic lesions, particularly in the CNS, remains scarce. Based on this context, this study aims to evaluate TROP2 expression in brain metastases from various solid tumors and compare it with expression in primary tumors. Materials and methods Case selection After the approval from the institutional review board (approval number: 2024AN0580), A total of 61 surgically resected brain metastasis specimen between 2015 to 2023 were retrieved for the pathology database of the Department of Pathology at the Anam Hospital, Korea University College of Medicine, Seoul, Republic of Korea. When available, corresponding primary tumor tissues were also collected. Clinical data, including the patient’s age, sex, origin of tumor was reviewed in the electronic medical records. Tissue microarray construction Tissue microarrays (TMAs) were constructed from formalin-fixed, paraffin-embedded tissue blocks by using a manual tissue micro-arrayer (UNITIMA, Seoul, South Korea). Areas occupied for > 75% of tumor cells without accompanying tumor necrosis were selected and two representative cores were punched out from a donor block and transferred into a new recipient block with a punch of a 3-mm diameter. Immunohistochemical staining The Immunoshistochemical (IHC) staining was performed as follows. Briefly, 4- µm tissue sections from TMAs were subjected to IHC using a Ventana auto-stainer and an ultra-Vies DAB Detection Kit (Ventana, Tucson, Arizona), according to the manufacturer’s instruction. Primary antibodies for TROP2 (EPR20043, catalog No. ab214488, rabbit monoclonal, 1:2000, Abcam, Cambridge, UK) were used. The TROP2 IHC staining was evaluated by two pathologists (YNS and YSK) and classified into 3 categories (Fig. 1 ): Diffuse positive (> 95%), focal positive (> 0% and < 95%), and negative. Statistical methods The R software (version 4.02, Vienna, Austria) was used. The association between TROP2 expression pattern and tumor origin, as well as between TROP2 expression pattern and pathologic diagnosis, was evaluated using the χ2 and/or Fisher’s exact tests. Survival analysis based on expression levels was performed using log rank test and Kaplan-Meier analysis. P-values less than 0.05 were considered statistically significant. Results Clinicopathological characteristics of cases A total of 61 surgically resected brain metastasis specimens were available for analysis. Table 1 summarizes the characteristics of cases. The mean age of the patients was 61.5 ± 10.0 years (range, 37 to 82 years) with a male-to-female ratio of 1.1. Metastatic brain tumors originating from various organs were included. The most common primary site was lung (23 cases, 37.7%), followed by the breast (11 cases, 18.0%) and the colorectum (10 cases, 16.4%). Other primary sites included the bladder and skin (3 cases each, 4.9%), kidney and ovary (2 cases each, 3.3%), and well as less common sites such as the ear, gallbladder, hypopharynx, thymus, and thyroid, each contributing 1 case (1.6%). In terms of pathologic diagnosis, adenocarcinoma was the most frequently observed type, with 27 cases (44.3%), followed by invasive ductal carcinoma with 11 cases (18.0%), Squamous cell carcinoma with 6 cases (9.8%), and undifferentiated carcinoma in 4 cases (6.6%). Melanoma and urothelial carcinoma were found in 3 cases each (4.9%). Less common diagnoses included clear cell carcinoma and high-grade serous carcinoma (2 cases each, 3.3%), along with adenoid cystic carcinoma, follicular carcinoma, and thymoma each present in 1 case (1.6%). Table 1 Clinicopathological characteristics of the analyzed cases Characteristics No. of patients % of patients Age (years) 61.5 ± 10.0 Sex Male 32 52.5 Female 29 47.5 Primary site Lung 23 37.7 Breast 11 18.0 Colorectal 10 16.4 Bladder 3 4.9 Skin 3 4.9 Kidney 2 3.3 Ovary 2 3.3 Unknown 2 3.3 Ear 1 1.6 Gallbladder 1 1.6 Hypopharynx 1 1.6 Thymus 1 1.6 Thyroid 1 1.6 Diagnosis Adenocarcinoma 27 44.3 Invasive ductal carcinoma 11 18.0 Squamous cell carcinoma 6 9.8 Carcinoma, undifferentiated 4 6.6 Melanoma 3 4.9 Urothelial carcinoma 3 4.9 Clear cell carcinoma 2 3.3 High-grade serous carcinoma 2 3.3 Adenoid cystic carcinoma 1 1.6 Follicular carcinoma 1 1.6 Thymoma 1 1.6 Median time to brain metastasis (months, range) 23.5 (0-137) Median overall survival (months, range) 40.3 (5–98) Median survival post-CNS metastasis (months, range) 9.9 (0–76) CNS metastasis number Single 37 60.7 Multiple 24 39.3 CNS metastasis treatment Surgery 61 100.0 Radiotherapy 31 50.8 TROP2 expression in metastatic and primary tumor Among the 61 metastatic brain tumors, TROP2 expression was diffusely positive in 38 cases (62.3%), focally positive in 10 cases (16.4%), and negative in 13 cases (21.3%, Fig. 2 A). Of the tumors with diffuse positive TROP2 expression, the most common site of origin was the lung (18 cases, 47.4%), followed by the breast (11 cases, 28.9%), bladder (3 cases, 7.9%), and ovary (2 cases, 5.3%). Single cases originated from colorectal, ear, gallbladder, and hypopharyngeal primaries. Among the tumors with focal TROP2 expression, 8 cases (80%) originated from colorectum, and 2 cases (20%) were from the lung. In the TROP2-negative cases, lung and skin tumors accounted for 3 cases each (23.1%), kidney and tumors of unknown origin accounted for 2 cases each (15.4%), and colorectal, thyroid, and thymic tumors each accounted for 1 case (7.7%, Fig. 2 B). The distribution of TROP2 expression according to pathologic diagnosis is illustrated in Fig. 2 C. Notably, in the most common tumor type, adenocarcinoma, TROP2 expression was diffusely positive in 15 cases (55.6%), focally positive in 9 cases (33.3%), and negative in 3 cases (11.1%). In contrast, all 11 cases of invasive breast carcinoma of no special type (IBC-NST) showed diffuse TROP2 positivity. Similarly, in primary tumors, TROP2 expression was diffusely positive in 10 cases (71.4%), focally positive in 2 cases (14.3%), and negative in 2 cases (14.3%, Fig. 2 D). Among the TROP2 diffuse positive cases, 3 cases (30%) originated from the lung, 2 cases (20%) each from the bladder and colorectum, and 1 case (10%) each from the hypopharynx, kidney, and ovary. For the focal TROP2 positive cases, both originated from colorectal primaries (100%). Among the TROP2-negative cases, 1 case (50%) originated from the colorectum and 1 case (50%) from the thyroid (Fig. 2 E). The distribution of TROP2 expression by pathologic diagnosis showed a pattern similar to that of brain metastatic lesions, with adenocarcinoma being the most common tumor type. In adenocarcinomas, TROP2 expression was diffusely positive in 4 cases (57.1%), focally positive in 2 cases (28.6%), and negative in 1 case (14.3%). All cases of squamous cell carcinoma, urothelial carcinoma, clear cell carcinoma, and high-grade serous carcinoma demonstrated diffuse TROP2 positivity, while follicular carcinoma was TROP2-negative. Detailed TROP2 expression according to tumor origin and pathologic diagnosis for both brain metastatic lesions and primary tumors are provided in Supplementary Tables 1 and 2 . Differences in TROP2 expression based on clinical characteristics We analyzed whether differences in TROP2 expression were associated with characteristics of CNS metastases or patient survival. Patients were categorized into two groups based on the presentation of CNS metastases at the time of diagnosis: single vs. multiple metastases. When stratified by TROP2 expression levels, the distribution was as follows: among patients with diffuse positive expression, 21 had single CNS metastasis, and 16 had multiple metastases. In the focal positive group, 8 had single CNS metastasis, and 2 had multiple metastases. Among patients with negative expression, 7 had single CNS metastasis, and 6 had multiple metastases. Fisher’s exact test did not reveal a significant association (p = 0.454). The median survival post-CNS metastasis was: diffuse positive, 76.4 months (95% CI: 46.8–NA); focal positive, 18.5 months (95% CI: 13.5–NA); and negative, 43.0 months (95% CI: 19.0–NA). The log-rank test again showed no significant differences (p = 0.218). HRs were 2.93 (95% CI: 0.72–11.94, p = 0.134) for focal positive relative to diffuse positive, and 1.97 (95% CI: 0.64–6.08, p = 0.237) for negative relative to diffuse positive. ( Fig. 3 ) Comparison of TROP2 Expression in paired primary and brain metastatic tumor Among the 14 cases where both primary tumors and corresponding brain metastases were available for paired TROP2 expression analysis, three cases (21.4%) showed differences in TROP2 expression between the primary and metastatic sites (Fig. 4 , Supplementary Table 3 ). Specifically, in colorectal adenocarcinoma, one case shifted from diffuse positive in the primary lesion to focal positive in the metastasis, and another case showed negative expression in the primary lesion but focal positivity in the metastasis. Additionally, a case of kidney clear cell carcinoma exhibited diffuse positive TROP2 expression in the primary tumor but was negative in the brain metastasis. The remaining 11 cases (78.6%) displayed consistent TROP2 expression patterns between the primary and metastatic lesions. Discussion This study provides important insights into the TROP2 expression in brain metastases across various primary tumor origins. Notably, the high prevalence of diffuse TROP2 positivity (62.3%) in brain metastases, particularly those originating from lung and breast cancers, highlights the potential role of TROP2 in the pathogenesis and progression of CNS metastasis. Anti-cancer therapies targeting TROP2 have predominantly focused on the development of ADC. A representative TROP2 ADC, sacituzumab govitecan (SG), consists of a TROP2-targeting antibody linked to the topoisomerase I inhibitor SN-38 via a cleavable linker, with a drug-antibody ratio of 1:8, demonstrating potent anti-cancer effects [ 16 ]. In the ASCENT phase 3 clinical trial, SG significantly improved median progression-free survival (mPFS; HR 0.41, 95% CI 0.32–0.52, P < 0.001) and median overall survival (mOS; HR 0.48, 95% CI 0.38–0.59, P < 0.001) in patients with advanced TNBC [ 12 ], leading to FDA approval. In the TROPiCS-02 trial, targeting HR+/HER2- breast cancer, SG also demonstrated a significant mOS benefit compared to the control group (HR 0.79, 95% CI 0.65–0.96, P = 0.020) [ 17 ]. Additionally, SG has shown therapeutic potential in minor cancer types, such as endometrial cancer, small cell lung cancer, and castration-resistant prostate cancer [ 18 ]. Based on these findings, numerous combination therapy clinical trials are currently underway [ 19 ]. Datopotamab deruxtecan (Dato-DXd) is another ADC that combines a TROP2 antibody with DXd, featuring a drug-to-antibody ratio of 1:4 [ 20 ]. In HR+/HER2- breast cancer, it demonstrated a significant improvement in mPFS compared to the control group (HR 0.63, 95% CI 0.52–0.76, P < .0001) [ 21 ]. In a phase 3 clinical trial for patients with advanced NSCLC, it also showed a significant mPFS benefit over docetaxel (HR 0.75, 95% CI 0.62–0.91, P = .004) [ 22 ]. Promising results have recently been reported in endometrial and ovarian cancer cohorts [ 23 ]. Additionally, other TROP2-targeting ADCs, such as SKB264, SHR-A1921, and LCB84, are undergoing early clinical trials based on encouraging preclinical data [ 24 – 26 ]. Preclinical studies suggest a potential correlation between TROP2 expression and the efficacy of ADCs. In breast cancer cell lines, increased TROP2 expression was associated with enhanced therapeutic activity of SG [ 27 ]. Similarly, clinical trials targeting TNBC demonstrated the greatest efficacy in patients with medium to high TROP2 expression, with objective response rates of 44%, 38%, and 22% for high, medium, and low expression levels, respectively [ 28 ]. However, clinical data across various cancer types remain limited, and due to the bystander effect of ADCs and the heterogeneity of TROP2 expression, definitive conclusions cannot yet be drawn. As cancer survival improves, recurrent CNS metastases following local treatment have become increasingly common, highlighting the need for effective systemic therapies. In cancers with high rates of brain metastases, such as breast and lung cancer, clinical trials now frequently include CNS-specific endpoints. Systemic treatment for CNS metastases remains challenging due to the BBB. While small molecules like TKIs have demonstrated CNS efficacy [ 29 , 30 ], larger agents like SG (160 kDa) face limited BBB penetration [ 31 ]. However, local BBB disruptions from metastases or radiotherapy may enable larger molecules to access CNS lesions, making target expression a critical determinant of efficacy. Our study supports this concept, with 78.7% of 61 brain metastases exhibiting diffuse or focal TROP2 expression. Consistency in TROP2 expression between primary and CNS lesions was observed in 78.6% of matched cases. These findings suggest a potential association between TROP2 expression and the efficacy of anti-TROP2 ADCs in CNS metastases, warranting further investigation. This study represents the largest cohort of brain metastases evaluated for TROP2 expression using standardized IHC. All staining was performed in a single center, with a single pathologist ensuring consistency, and the analysis was blinded to treatment data to minimize bias. Previous studies evaluating TROP2 expression in various cancers, including breast [ 3 , 32 , 33 ], colorectal [ 4 , 5 ], skin [ 8 , 34 ], and pancreas [ 9 ], primarily used semi-quantitative assessment methods such as H-score to evaluate TROP2 expression levels. These studies often relied on specific scoring thresholds to categorize TROP2 expression. In contrast, our study demonstrated a relatively clear differentiation of TROP2 expression into diffuse, focal, and negative patterns, allowing for straightforward analysis without the need for further intensity or area-based categorization. It is important to note that factors such as the type of antibody used and the application of tissue microarrays (TMAs) may have influenced the observed TROP2 expression patterns. While TMAs are valuable for high-throughput analysis, they may not fully capture the tumor heterogeneity present in whole-tumor sections. Therefore, future studies examining cases with changes in TROP2 expression between primary and metastatic lesions, or those showing focal positivity, would benefit from evaluating TROP2 expression using whole-slide sections to better reflect the full spectrum of tumor heterogeneity. Comprehensive clinical data enabled robust correlations with TROP2 expression. However, the inclusion of diverse tumor types limited subgroup analyses, and the lack of data from visceral metastases prevents conclusions about the specificity of TROP2 expression to CNS lesions. Furthermore, as samples were collected before TROP2 ADCs became available, intracranial efficacy based on TROP2 expression could not be assessed. Further studies are required to validate these findings. In conclusion, this study demonstrated variable TROP2 expression in 61 brain metastasis samples and confirmed high consistency of TROP2 expression between primary and brain metastatic lesions. While promising, further research is required to validate the clinical efficacy of anti-TROP2 therapies in patients with CNS metastases. Abbreviations TROP2 trophoblast cell surface antigen 2 CNS central nervous system ADCs antibody-drug conjugates SG Sacituzumab govitecan OS overall survival TNBC triple-negative breast cancer BBB blood-brain barrier IBC-NST invasive breast carcinoma of no special type Declarations Ethics approval and consent to participants This study was approved by the Institutional Review Board of Korea University Anam Hospital (IRB No. 2024AN0580), which waived the requirement for informed consent due to the retrospective design, in accordance with the Bioethics and Safety Act. All procedures were conducted in accordance with institutional guidelines and the Declaration of Helsinki. Consent for publication Not applicable Availability of data and materials The dataset generated and/or analyzed during this study is available from the corresponding author upon reasonable request. Competing interest The authors have no conflict of interest in the study. Funding No funding was received for this study. Author contributions The concept of the study was designed by JWK. JWL, JHK, SHL, YJC, and KHP. JS and HO collected data for the study. YNS and JWK analyzed and visualized the data. YNS and JWK drafted the manuscript. All the authors have reviewed and approved the submitted data. References Shvartsur A, Bonavida B. Trop2 and its overexpression in cancers: regulation and clinical/therapeutic implications. Genes Cancer. 2015;6(3–4):84–105. Ripani E, Sacchetti A, Corda D, Alberti S. Human Trop-2 is a tumor-associated calcium signal transducer. Int J Cancer. 1998;76(5):671–6. Ambrogi F, Fornili M, Boracchi P, Trerotola M, Relli V, Simeone P, et al. Trop-2 is a determinant of breast cancer survival. PLoS ONE. 2014;9(5):e96993. Moretto R, Germani MM, Giordano M, Conca V, Proietti A, Niccoli C, et al. Trop-2 and Nectin-4 immunohistochemical expression in metastatic colorectal cancer: searching for the right population for drugs' development. Br J Cancer. 2023;128(7):1391–9. 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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-6747270","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":474316075,"identity":"58c63525-00b4-478c-9803-65453df09ba8","order_by":0,"name":"You-Na Sung","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"You-Na","middleName":"","lastName":"Sung","suffix":""},{"id":474316076,"identity":"c9240740-f64c-460d-9bab-21252576fc70","order_by":1,"name":"Jongmin Sim","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Jongmin","middleName":"","lastName":"Sim","suffix":""},{"id":474316077,"identity":"6ae88b5a-3a7e-454c-978f-58eb2691824d","order_by":2,"name":"Harim Oh","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Harim","middleName":"","lastName":"Oh","suffix":""},{"id":474316078,"identity":"fa334454-8abf-484e-8250-70b956899264","order_by":3,"name":"Ji Won Lee","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Ji","middleName":"Won","lastName":"Lee","suffix":""},{"id":474316079,"identity":"a76f4972-56c3-4f14-aa98-48458feb2f19","order_by":4,"name":"Jwa Hoon Kim","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Jwa","middleName":"Hoon","lastName":"Kim","suffix":""},{"id":474316080,"identity":"5745c56d-2259-41a2-90d9-67b024120996","order_by":5,"name":"Soohyeon Lee","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Soohyeon","middleName":"","lastName":"Lee","suffix":""},{"id":474316081,"identity":"1da994f1-ee48-4495-be48-b7dd512db4cd","order_by":6,"name":"Yoon Ji Choi","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Yoon","middleName":"Ji","lastName":"Choi","suffix":""},{"id":474316082,"identity":"dad898f0-778f-4862-b490-bd382c44c8ae","order_by":7,"name":"Kyong Hwa Park","email":"","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":false,"prefix":"","firstName":"Kyong","middleName":"Hwa","lastName":"Park","suffix":""},{"id":474316083,"identity":"add1a65b-9864-411e-846b-b75fa674d7b5","order_by":8,"name":"Ju Won Kim","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIie3RsQrCMBCA4SsBXQ5cLYo+gWAodNRXaSjEpYJjQcEUoS4+QH0RZ6XQLnmAipMUXB3cxSiikyGjQ/4lcMcHBwGw2f4wR7yeAKGZfobEkGBhSN4FAG1uSEgW0XoGvDvYXlgdxyNorffEi3WHZZHnZRChf+I5lTKEtgwIk1oy3XUQYkUmqZuk6qYKyEEYkWOpyH0JfUOiDqsahZuIHIaKMC3ZXG8eAkdf8pCKokQq2YrqCF1zViOEY78s6Fks5r1emeeuljyXzv07wM/3/qqv3dpsNpvt2QPwdkX9ygniYwAAAABJRU5ErkJggg==","orcid":"","institution":"Korea University Anam Hospital, Korea University College of Medicine","correspondingAuthor":true,"prefix":"","firstName":"Ju","middleName":"Won","lastName":"Kim","suffix":""}],"badges":[],"createdAt":"2025-05-26 05:38:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6747270/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6747270/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":85268545,"identity":"4c7a2d9b-2755-40dd-bd44-a64940f54c35","added_by":"auto","created_at":"2025-06-24 06:06:57","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":262033,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative images of TROP2 immunohistochemical (IHC) staining in metastatic brain tumor. \u003cstrong\u003e(A)\u003c/strong\u003eMetastatic invasive breast carcinoma, no special type showing diffuse TROP2 positivity (×200, ×40 inlet). \u003cstrong\u003e(B)\u003c/strong\u003e Metastatic adenocarcinoma from the colon showing TROP2 focal positivity (×400, ×40 inlet). \u003cstrong\u003e(C) \u003c/strong\u003eMetastatic follicular carcinoma from the thyroid showing TROP2 negativity (×200, ×40 inlet).\u003c/p\u003e","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/ede2be8556457d79e93db261.png"},{"id":85268542,"identity":"029454a8-7dc9-4042-a89b-31e6bae54784","added_by":"auto","created_at":"2025-06-24 06:06:57","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":33846,"visible":true,"origin":"","legend":"\u003cp\u003eTROP2 expression in metastatic brain and primary tumors. \u003cstrong\u003e(A) \u003c/strong\u003ePie chart showing TROP2 expression pattern in metastatic brain tumors. \u003cstrong\u003e(B, C) \u003c/strong\u003eBar chart showing TROP2 expression in metastatic brain tumor according to origin and diagnosis. \u003cstrong\u003e(D) \u003c/strong\u003ePie chart showing TROP2 expression pattern in primary tumors. \u003cstrong\u003e(E, F) \u003c/strong\u003eBar chart showing TROP2 expression in primary tumor according to origin and diagnosis.\u003c/p\u003e","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/43e15bc3feb9ae74732eb581.png"},{"id":85268540,"identity":"f7662343-655e-419c-9123-2666d8754fb8","added_by":"auto","created_at":"2025-06-24 06:06:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":27536,"visible":true,"origin":"","legend":"\u003cp\u003eKaplan–Meier analysis for post-CNS survival stratified by TROP2 expression levels.\u003c/p\u003e","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/6a03728a6c2b01e1dfdc0b84.png"},{"id":85269545,"identity":"e8bafc5f-0201-49cc-82ef-0f4e01733b94","added_by":"auto","created_at":"2025-06-24 06:14:57","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":27062,"visible":true,"origin":"","legend":"\u003cp\u003eSankey diagram illustrating the flow of TROP2 expression between primary and metastatic tumors\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/7931365365991c05c94af45c.png"},{"id":87731945,"identity":"6b137764-a2e2-44a5-a876-71263579b24f","added_by":"auto","created_at":"2025-07-28 11:47:10","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1134181,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/a97ba44a-b028-4f3f-b4fe-63f3419232d2.pdf"},{"id":85268543,"identity":"53f0102b-c7f5-4a61-aabf-225206ee4767","added_by":"auto","created_at":"2025-06-24 06:06:57","extension":"xlsx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":17593,"visible":true,"origin":"","legend":"","description":"","filename":"Trop2MetaSupple.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-6747270/v1/c08420efa3f74802bd479d5f.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparative immunohistochemical expression of TROP2 in brain metastatic and primary tumors","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe human trophoblast cell surface antigen 2 (TROP2) is a transmembrane glycoprotein that acts as an intracellular calcium signal transducer, driving self-renewal, cell proliferation, invasion, and survival [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. It is overexpressed in various solid tumors, including breast [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], Colorectal [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], lung [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], gastric [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], skin [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], and pancreatic cancers [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], with expression reported in 55\u0026ndash;75% of cases. Overexpression of TROP2 is generally associated to poor prognosis, increased tumor aggressiveness, and higher metastatic potential [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMetastatic solid tumors remain a significant unmet medical challenge, particularly central nervous system (CNS) metastases, which are associated with extremely poor outcomes. While targeted therapies, such as monoclonal antibodies and antibody-drug conjugates (ADCs), have improved outcomes in advanced cancer, their efficacy against CNS metastases is limited. Sacituzumab govitecan (SG), a TROP2-directed ADC, has demonstrated significant overall survival (OS) benefits in patients with triple-negative breast cancer (TNBC) [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] but showed no OS improvement for those with CNS metastases [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The prevailing explanation attributes this limitation to the inability of these therapies to effectively penetrate the blood-brain barrier (BBB) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. However, the distinct molecular and genomic features of CNS metastases, which often diverge from those of the primary tumor, must also be considered [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eResearch on TROP2 heterogeneity between primary and metastatic lesions, particularly in the CNS, remains scarce. Based on this context, this study aims to evaluate TROP2 expression in brain metastases from various solid tumors and compare it with expression in primary tumors.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eCase selection\u003c/h2\u003e \u003cp\u003eAfter the approval from the institutional review board (approval number: 2024AN0580), A total of 61 surgically resected brain metastasis specimen between 2015 to 2023 were retrieved for the pathology database of the Department of Pathology at the Anam Hospital, Korea University College of Medicine, Seoul, Republic of Korea. When available, corresponding primary tumor tissues were also collected. Clinical data, including the patient\u0026rsquo;s age, sex, origin of tumor was reviewed in the electronic medical records.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eTissue microarray construction\u003c/h3\u003e\n\u003cp\u003eTissue microarrays (TMAs) were constructed from formalin-fixed, paraffin-embedded tissue blocks by using a manual tissue micro-arrayer (UNITIMA, Seoul, South Korea). Areas occupied for \u0026gt;\u0026thinsp;75% of tumor cells without accompanying tumor necrosis were selected and two representative cores were punched out from a donor block and transferred into a new recipient block with a punch of a 3-mm diameter.\u003c/p\u003e\n\u003ch3\u003eImmunohistochemical staining\u003c/h3\u003e\n\u003cp\u003eThe Immunoshistochemical (IHC) staining was performed as follows. Briefly, 4- \u0026micro;m tissue sections from TMAs were subjected to IHC using a Ventana auto-stainer and an ultra-Vies DAB Detection Kit (Ventana, Tucson, Arizona), according to the manufacturer\u0026rsquo;s instruction. Primary antibodies for TROP2 (EPR20043, catalog No. ab214488, rabbit monoclonal, 1:2000, Abcam, Cambridge, UK) were used. The TROP2 IHC staining was evaluated by two pathologists (YNS and YSK) and classified into 3 categories (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e): Diffuse positive (\u0026gt;\u0026thinsp;95%), focal positive (\u0026gt;\u0026thinsp;0% and \u0026lt;\u0026thinsp;95%), and negative.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eStatistical methods\u003c/h3\u003e\n\u003cp\u003eThe R software (version 4.02, Vienna, Austria) was used. The association between TROP2 expression pattern and tumor origin, as well as between TROP2 expression pattern and pathologic diagnosis, was evaluated using the χ2 and/or Fisher\u0026rsquo;s exact tests. Survival analysis based on expression levels was performed using log rank test and Kaplan-Meier analysis. P-values less than 0.05 were considered statistically significant.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eClinicopathological characteristics of cases\u003c/h2\u003e \u003cp\u003eA total of 61 surgically resected brain metastasis specimens were available for analysis. Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes the characteristics of cases. The mean age of the patients was 61.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0 years (range, 37 to 82 years) with a male-to-female ratio of 1.1. Metastatic brain tumors originating from various organs were included. The most common primary site was lung (23 cases, 37.7%), followed by the breast (11 cases, 18.0%) and the colorectum (10 cases, 16.4%). Other primary sites included the bladder and skin (3 cases each, 4.9%), kidney and ovary (2 cases each, 3.3%), and well as less common sites such as the ear, gallbladder, hypopharynx, thymus, and thyroid, each contributing 1 case (1.6%). In terms of pathologic diagnosis, adenocarcinoma was the most frequently observed type, with 27 cases (44.3%), followed by invasive ductal carcinoma with 11 cases (18.0%), Squamous cell carcinoma with 6 cases (9.8%), and undifferentiated carcinoma in 4 cases (6.6%). Melanoma and urothelial carcinoma were found in 3 cases each (4.9%). Less common diagnoses included clear cell carcinoma and high-grade serous carcinoma (2 cases each, 3.3%), along with adenoid cystic carcinoma, follicular carcinoma, and thymoma each present in 1 case (1.6%).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinicopathological characteristics of the analyzed cases\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCharacteristics\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNo. of patients\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e% of patients\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eAge (years)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e61.5\u0026thinsp;\u0026plusmn;\u0026thinsp;10.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eSex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e52.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e47.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003ePrimary site\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLung\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBreast\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eColorectal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSkin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKidney\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOvary\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnknown\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGallbladder\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHypopharynx\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThymus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThyroid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eDiagnosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdenocarcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e44.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInvasive ductal carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSquamous cell carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCarcinoma, undifferentiated\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMelanoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUrothelial carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eClear cell carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eHigh-grade serous carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdenoid cystic carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eFollicular carcinoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eThymoma\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMedian time to brain metastasis (months, range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e23.5 (0-137)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMedian overall survival (months, range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e40.3 (5\u0026ndash;98)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eMedian survival post-CNS metastasis (months, range)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e9.9 (0\u0026ndash;76)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCNS metastasis number\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSingle\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e60.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMultiple\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e24\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e39.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eCNS metastasis treatment\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSurgery\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eRadiotherapy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eTROP2 expression in metastatic and primary tumor\u003c/h3\u003e\n\u003cp\u003eAmong the 61 metastatic brain tumors, TROP2 expression was diffusely positive in 38 cases (62.3%), focally positive in 10 cases (16.4%), and negative in 13 cases (21.3%, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Of the tumors with diffuse positive TROP2 expression, the most common site of origin was the lung (18 cases, 47.4%), followed by the breast (11 cases, 28.9%), bladder (3 cases, 7.9%), and ovary (2 cases, 5.3%). Single cases originated from colorectal, ear, gallbladder, and hypopharyngeal primaries. Among the tumors with focal TROP2 expression, 8 cases (80%) originated from colorectum, and 2 cases (20%) were from the lung. In the TROP2-negative cases, lung and skin tumors accounted for 3 cases each (23.1%), kidney and tumors of unknown origin accounted for 2 cases each (15.4%), and colorectal, thyroid, and thymic tumors each accounted for 1 case (7.7%, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). The distribution of TROP2 expression according to pathologic diagnosis is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC. Notably, in the most common tumor type, adenocarcinoma, TROP2 expression was diffusely positive in 15 cases (55.6%), focally positive in 9 cases (33.3%), and negative in 3 cases (11.1%). In contrast, all 11 cases of invasive breast carcinoma of no special type (IBC-NST) showed diffuse TROP2 positivity. Similarly, in primary tumors, TROP2 expression was diffusely positive in 10 cases (71.4%), focally positive in 2 cases (14.3%), and negative in 2 cases (14.3%, Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD). Among the TROP2 diffuse positive cases, 3 cases (30%) originated from the lung, 2 cases (20%) each from the bladder and colorectum, and 1 case (10%) each from the hypopharynx, kidney, and ovary. For the focal TROP2 positive cases, both originated from colorectal primaries (100%). Among the TROP2-negative cases, 1 case (50%) originated from the colorectum and 1 case (50%) from the thyroid (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE). The distribution of TROP2 expression by pathologic diagnosis showed a pattern similar to that of brain metastatic lesions, with adenocarcinoma being the most common tumor type. In adenocarcinomas, TROP2 expression was diffusely positive in 4 cases (57.1%), focally positive in 2 cases (28.6%), and negative in 1 case (14.3%). All cases of squamous cell carcinoma, urothelial carcinoma, clear cell carcinoma, and high-grade serous carcinoma demonstrated diffuse TROP2 positivity, while follicular carcinoma was TROP2-negative. Detailed TROP2 expression according to tumor origin and pathologic diagnosis for both brain metastatic lesions and primary tumors are provided in \u003cb\u003eSupplementary Tables\u0026nbsp;1 and 2\u003c/b\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eDifferences in TROP2 expression based on clinical characteristics\u003c/h3\u003e\n\u003cp\u003eWe analyzed whether differences in TROP2 expression were associated with characteristics of CNS metastases or patient survival. Patients were categorized into two groups based on the presentation of CNS metastases at the time of diagnosis: single vs. multiple metastases.\u003c/p\u003e \u003cp\u003eWhen stratified by TROP2 expression levels, the distribution was as follows: among patients with diffuse positive expression, 21 had single CNS metastasis, and 16 had multiple metastases. In the focal positive group, 8 had single CNS metastasis, and 2 had multiple metastases. Among patients with negative expression, 7 had single CNS metastasis, and 6 had multiple metastases. Fisher\u0026rsquo;s exact test did not reveal a significant association (p\u0026thinsp;=\u0026thinsp;0.454).\u003c/p\u003e \u003cp\u003eThe median survival post-CNS metastasis was: diffuse positive, 76.4 months (95% CI: 46.8\u0026ndash;NA); focal positive, 18.5 months (95% CI: 13.5\u0026ndash;NA); and negative, 43.0 months (95% CI: 19.0\u0026ndash;NA). The log-rank test again showed no significant differences (p\u0026thinsp;=\u0026thinsp;0.218). HRs were 2.93 (95% CI: 0.72\u0026ndash;11.94, p\u0026thinsp;=\u0026thinsp;0.134) for focal positive relative to diffuse positive, and 1.97 (95% CI: 0.64\u0026ndash;6.08, p\u0026thinsp;=\u0026thinsp;0.237) for negative relative to diffuse positive. \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eComparison of TROP2 Expression in paired primary and brain metastatic tumor\u003c/h2\u003e \u003cp\u003eAmong the 14 cases where both primary tumors and corresponding brain metastases were available for paired TROP2 expression analysis, three cases (21.4%) showed differences in TROP2 expression between the primary and metastatic sites (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cb\u003eSupplementary Table\u0026nbsp;3\u003c/b\u003e). Specifically, in colorectal adenocarcinoma, one case shifted from diffuse positive in the primary lesion to focal positive in the metastasis, and another case showed negative expression in the primary lesion but focal positivity in the metastasis. Additionally, a case of kidney clear cell carcinoma exhibited diffuse positive TROP2 expression in the primary tumor but was negative in the brain metastasis. The remaining 11 cases (78.6%) displayed consistent TROP2 expression patterns between the primary and metastatic lesions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study provides important insights into the TROP2 expression in brain metastases across various primary tumor origins. Notably, the high prevalence of diffuse TROP2 positivity (62.3%) in brain metastases, particularly those originating from lung and breast cancers, highlights the potential role of TROP2 in the pathogenesis and progression of CNS metastasis.\u003c/p\u003e \u003cp\u003eAnti-cancer therapies targeting TROP2 have predominantly focused on the development of ADC. A representative TROP2 ADC, sacituzumab govitecan (SG), consists of a TROP2-targeting antibody linked to the topoisomerase I inhibitor SN-38 via a cleavable linker, with a drug-antibody ratio of 1:8, demonstrating potent anti-cancer effects [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In the ASCENT phase 3 clinical trial, SG significantly improved median progression-free survival (mPFS; HR 0.41, 95% CI 0.32\u0026ndash;0.52, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and median overall survival (mOS; HR 0.48, 95% CI 0.38\u0026ndash;0.59, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) in patients with advanced TNBC [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], leading to FDA approval. In the TROPiCS-02 trial, targeting HR+/HER2- breast cancer, SG also demonstrated a significant mOS benefit compared to the control group (HR 0.79, 95% CI 0.65\u0026ndash;0.96, P\u0026thinsp;=\u0026thinsp;0.020) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Additionally, SG has shown therapeutic potential in minor cancer types, such as endometrial cancer, small cell lung cancer, and castration-resistant prostate cancer [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Based on these findings, numerous combination therapy clinical trials are currently underway [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDatopotamab deruxtecan (Dato-DXd) is another ADC that combines a TROP2 antibody with DXd, featuring a drug-to-antibody ratio of 1:4 [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In HR+/HER2- breast cancer, it demonstrated a significant improvement in mPFS compared to the control group (HR 0.63, 95% CI 0.52\u0026ndash;0.76, P\u0026thinsp;\u0026lt;\u0026thinsp;.0001) [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In a phase 3 clinical trial for patients with advanced NSCLC, it also showed a significant mPFS benefit over docetaxel (HR 0.75, 95% CI 0.62\u0026ndash;0.91, P\u0026thinsp;=\u0026thinsp;.004) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Promising results have recently been reported in endometrial and ovarian cancer cohorts [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Additionally, other TROP2-targeting ADCs, such as SKB264, SHR-A1921, and LCB84, are undergoing early clinical trials based on encouraging preclinical data [\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePreclinical studies suggest a potential correlation between TROP2 expression and the efficacy of ADCs. In breast cancer cell lines, increased TROP2 expression was associated with enhanced therapeutic activity of SG [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Similarly, clinical trials targeting TNBC demonstrated the greatest efficacy in patients with medium to high TROP2 expression, with objective response rates of 44%, 38%, and 22% for high, medium, and low expression levels, respectively [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, clinical data across various cancer types remain limited, and due to the bystander effect of ADCs and the heterogeneity of TROP2 expression, definitive conclusions cannot yet be drawn.\u003c/p\u003e \u003cp\u003eAs cancer survival improves, recurrent CNS metastases following local treatment have become increasingly common, highlighting the need for effective systemic therapies. In cancers with high rates of brain metastases, such as breast and lung cancer, clinical trials now frequently include CNS-specific endpoints. Systemic treatment for CNS metastases remains challenging due to the BBB. While small molecules like TKIs have demonstrated CNS efficacy [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], larger agents like SG (160 kDa) face limited BBB penetration [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. However, local BBB disruptions from metastases or radiotherapy may enable larger molecules to access CNS lesions, making target expression a critical determinant of efficacy. Our study supports this concept, with 78.7% of 61 brain metastases exhibiting diffuse or focal TROP2 expression. Consistency in TROP2 expression between primary and CNS lesions was observed in 78.6% of matched cases. These findings suggest a potential association between TROP2 expression and the efficacy of anti-TROP2 ADCs in CNS metastases, warranting further investigation.\u003c/p\u003e \u003cp\u003eThis study represents the largest cohort of brain metastases evaluated for TROP2 expression using standardized IHC. All staining was performed in a single center, with a single pathologist ensuring consistency, and the analysis was blinded to treatment data to minimize bias. Previous studies evaluating TROP2 expression in various cancers, including breast [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], colorectal [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], skin [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], and pancreas [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], primarily used semi-quantitative assessment methods such as H-score to evaluate TROP2 expression levels. These studies often relied on specific scoring thresholds to categorize TROP2 expression. In contrast, our study demonstrated a relatively clear differentiation of TROP2 expression into diffuse, focal, and negative patterns, allowing for straightforward analysis without the need for further intensity or area-based categorization. It is important to note that factors such as the type of antibody used and the application of tissue microarrays (TMAs) may have influenced the observed TROP2 expression patterns. While TMAs are valuable for high-throughput analysis, they may not fully capture the tumor heterogeneity present in whole-tumor sections. Therefore, future studies examining cases with changes in TROP2 expression between primary and metastatic lesions, or those showing focal positivity, would benefit from evaluating TROP2 expression using whole-slide sections to better reflect the full spectrum of tumor heterogeneity.\u003c/p\u003e \u003cp\u003eComprehensive clinical data enabled robust correlations with TROP2 expression. However, the inclusion of diverse tumor types limited subgroup analyses, and the lack of data from visceral metastases prevents conclusions about the specificity of TROP2 expression to CNS lesions. Furthermore, as samples were collected before TROP2 ADCs became available, intracranial efficacy based on TROP2 expression could not be assessed. Further studies are required to validate these findings.\u003c/p\u003e \u003cp\u003eIn conclusion, this study demonstrated variable TROP2 expression in 61 brain metastasis samples and confirmed high consistency of TROP2 expression between primary and brain metastatic lesions. While promising, further research is required to validate the clinical efficacy of anti-TROP2 therapies in patients with CNS metastases.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eTROP2\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;trophoblast cell surface antigen 2\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCNS\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;central nervous system\u003c/p\u003e\n\u003cp\u003eADCs\u0026nbsp;\u0026nbsp;antibody-drug conjugates\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSG\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Sacituzumab govitecan\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOS\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;overall survival\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTNBC\u0026nbsp;triple-negative breast cancer\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBBB\u0026nbsp; \u0026nbsp;\u0026nbsp;blood-brain barrier\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIBC-NST\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;invasive breast carcinoma of no special type\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participants\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Institutional Review Board of Korea University Anam Hospital (IRB No. 2024AN0580), which waived the requirement for informed consent due to the retrospective design, in accordance with the Bioethics and Safety Act.\u0026nbsp;All procedures were conducted in accordance with institutional guidelines and the Declaration of Helsinki.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dataset generated and/or analyzed during this study is available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no conflict of interest in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo funding was received for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe concept of the study was designed by JWK. JWL, JHK, SHL, YJC, and KHP. JS and HO collected data for the study. YNS and JWK analyzed and visualized the data. YNS and JWK drafted the manuscript. All the authors have reviewed and approved the submitted data.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eShvartsur A, Bonavida B. Trop2 and its overexpression in cancers: regulation and clinical/therapeutic implications. Genes Cancer. 2015;6(3\u0026ndash;4):84\u0026ndash;105.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRipani E, Sacchetti A, Corda D, Alberti S. Human Trop-2 is a tumor-associated calcium signal transducer. Int J Cancer. 1998;76(5):671\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAmbrogi F, Fornili M, Boracchi P, Trerotola M, Relli V, Simeone P, et al. Trop-2 is a determinant of breast cancer survival. 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Cancer Res. 2023;83(8Suppl):LB030.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim H, Guerra E, Baek E, Jeong Y, You H, Yu B et al. LCB84, a TROP2-targeted ADC, for treatment of solid tumors that express TROP-2 using the hu2G10 tumor-selective anti-TROP2 monoclonal antibody, a proprietary site-directed conjugation technology and plasma-stable tumor-selective linker chemistry. Cancer Res. 2022;82(12_Suppl):328.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCardillo TM, Rossi DL, Zalath MB, Liu D, Arrojo R, Sharkey RM, et al. Predictive biomarkers for sacituzumab govitecan efficacy in Trop-2-expressing triple-negative breast cancer. Oncotarget. 2020;11(43):3849\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao M, DiPeri TP, Raso MG, Zheng X, Rizvi YQ, Evans KW, et al. Epigenetically upregulating TROP2 and SLFN11 enhances therapeutic efficacy of TROP2 antibody drug conjugate sacitizumab govitecan. npj Breast Cancer. 2023;9(1):66.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLee B, Ji W, Lee JC, Song SY, Shin YS, Cho YH, et al. Efficacy of lazertinib for symptomatic or asymptomatic brain metastases in treatment-naive patients with advanced EGFR mutation-positive non-small cell lung cancer: Protocol of an open-label, single-arm phase II trial. Thorac Cancer. 2023;14(22):2233\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLin NU, Borges V, Anders C, Murthy RK, Paplomata E, Hamilton E, et al. Intracranial Efficacy and Survival With Tucatinib Plus Trastuzumab and Capecitabine for Previously Treated HER2-Positive Breast Cancer With Brain Metastases in the HER2CLIMB Trial. J Clin Oncol. 2020;38(23):2610\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNakhjavani M, Samarasinghe RM, Shigdar S. Triple-negative breast cancer brain metastasis: An update on druggable targets, current clinical trials, and future treatment options. Drug Discov Today. 2022;27(5):1298\u0026ndash;314.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJeon Y, Jo U, Hong J, Gong G, Lee HJ. Trophoblast cell-surface antigen 2 (TROP2) expression in triple-negative breast cancer. BMC Cancer. 2022;22(1):1014.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMertens RB, Makhoul EP, Li X, Dadmanesh F. Comparative expression of trophoblast cell-surface antigen 2 (TROP2) in the different molecular subtypes of invasive breast carcinoma: An immunohistochemical study of 94 therapy-naive primary breast tumors. Ann Diagn Pathol. 2024;68:152226.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTanegashima K, Tanaka Y, Ito T, Oda Y, Nakahara T. TROP2 Expression and Therapeutic Implications in Cutaneous Squamous Cell Carcinoma: Insights From Immunohistochemical and Functional Analysis. Exp Dermatol. 2024;33(10):e15196.\u003c/span\u003e\u003c/li\u003e\u003c/ol\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":"TROP2, Brain metastasis, Immunohistochemistry, Cancer, Primary tumor","lastPublishedDoi":"10.21203/rs.3.rs-6747270/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6747270/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eTROP2 overexpression was reported to predict poor prognosis and increased metastatic potential. This study evaluates TROP2 expression in brain metastases from diverse solid tumors and its consistency with primary tumors, addressing the limited research on TROP2 heterogeneity and its implications for CNS-targeted therapies.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTROP2 immunohistochemical staining was performed on 61 brain metastatic tumors and 14 corresponding primary tumors. Based on TROP2 expression, cases were categorized into three groups: diffuse positive (\u0026gt;\u0026thinsp;95%), focal positive (0\u0026ndash;95%), and negative (0%).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eAmong the 61 brain metastatic tumors, TROP2 expression was diffusely positive in 62.3%, focally positive in 16.4%, and negative in 21.3%. Diffuse TROP2 positivity was most observed in tumors of lung origin, while focal positivity was predominant in colorectal metastases. In terms of pathologic diagnosis, adenocarcinoma was the most common type, with 55.6% showing diffuse positivity, 33.3% showing focal positivity, and 11.1% showing negativity. Notably, all cases of invasive breast carcinoma of no special type (IBC-NST) exhibited diffuse TROP2 positivity. No significant association was found between TROP2 expression levels and post-CNS metastasis survival. In the paired analysis of 14 cases with both primary and metastatic tumors, TROP2 expression was consistent between primary and metastatic sites in 78.6% of cases. However, 21.4% of cases, including colorectal adenocarcinoma and kidney clear cell carcinoma, showed discordant expression patterns between the primary and metastatic lesions.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThis study demonstrated variable TROP2 expression in brain metastasis samples and confirmed high consistency of TROP2 expression between primary and brain metastatic lesions.\u003c/p\u003e","manuscriptTitle":"Comparative immunohistochemical expression of TROP2 in brain metastatic and primary tumors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-24 06:06:52","doi":"10.21203/rs.3.rs-6747270/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":"75276954-acbb-4072-a6af-eec6d59ea526","owner":[],"postedDate":"June 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-28T11:39:03+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-24 06:06:52","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6747270","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6747270","identity":"rs-6747270","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}