Polymorphous adenocarcinoma-like tumor of the breast: The first case report from Japan

Polymorphous adenocarcinoma-like tumor of the breast: The first case report from Japan | 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 Research Article Polymorphous adenocarcinoma-like tumor of the breast: The first case report from Japan Yuki Hara, Puay Hoon Tan, Foschini Maria Pia, Hiroshi Yano, Saki Sawada, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6075271/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 03 May, 2025 Read the published version in Breast Cancer → Version 1 posted 5 You are reading this latest preprint version Abstract Polymorphous adenocarcinoma-like (PmA-like) tumor of the breast is a rare salivary gland-like neoplasm, with few cases reported globally. We present the first case of a PmA-like tumor with a fibrous pseudocapsule from Japan, including radiological findings. A 40-year-old premenopausal woman presented with a painful mass in the right breast. Mammography revealed a high-density oval mass with predominantly circumscribed margins, while ultrasonography showed a hypoechoic oval mass with heterogeneous internal echoes and vascularity. Both imaging modalities suggested malignancy, prompting a vacuum assisted biopsy. Histopathological evaluation demonstrated diverse growth patterns and positivity for cytokeratin (CK) 7 and Bcl-2. Initially diagnosed as an unusual ductal proliferation, malignancy could not be excluded, leading to lumpectomy. The resected tumor measured 26 mm, exhibited a fibrous pseudocapsule with focal disruption, and showed varied histological patterns, including solid, cribriform, glandular, and cord-like structures. Immunohistochemistry revealed expression of CK7, S100, vimentin, CK5/6, E-cadherin, Bcl-2, p63, and smooth muscle actin (SMA), with no expression of p40, estrogen receptor, progesterone receptor, HER2, c-Kit, or androgen receptor. These findings, including penetration beyond the capsule, supported the diagnosis of an invasive PmA-like tumor of the breast. Following surgery, the patient underwent additional resection and sentinel lymph node biopsy due to a positive margin. No residual tumor or nodal metastases were found. The patient declined adjuvant therapy and remains recurrence-free after 26 months of follow-up. PmA-like tumors of the breast present diagnostic challenges due to their rarity and diverse histopathological features. Further studies are necessary to characterize their clinical behavior and guide management strategies. Breast polymorphous adenocarcinoma rare tumor salivary gland Figures Figure 1 Figure 2 Figure 3 Introduction Polymorphous adenocarcinoma-like (PmA-like) tumor of the breast is an exceptionally rare neoplasm with histological features resembling salivary gland tumors. According to the World Health Organization (WHO), PmA of the breast is characterized histopathologically by a proliferation of monotonous neoplastic cells with architectural diversity. These cells are arranged in a variety of patterns, including large nests surrounded by cords and single files ( 1 ). To date, only four cases of PmA-like tumor of the breast have been reported in the literature ( 2 , 3 ). All previously documented cases exhibited a triple-negative phenotype, as they were negative for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Immunohistochemical (IHC) analyses demonstrated positivity for cytokeratin (CK) 7 and Bcl-2, with negativity for p63 and alpha-smooth muscle actin (SMA). Herein, we present the first reported case in Japan of an invasive PmA-like tumor of the breast with a fibrous pseudocapsule. Uniquely, this case demonstrated heterogeneous weak to moderate immunoreactivity for p63 and SMA, alongside findings consistent with previously reported cases. Case presentation A 40-year-old premenopausal woman presented with a painful mass in her right breast that had appeared a few days prior. She had no significant medical or family history and had experienced one pregnancy and childbirth. Physical examination revealed no visible skin changes. Digital breast tomosynthesis (DBT) identified a 26 mm high-density oval mass with predominantly circumscribed but partially obscured margins in the middle-outer region of the right breast. No calcifications or axillary lymphadenopathy were observed. The lesion was assigned a Breast Imaging Reporting and Data System (BI-RADS) score of 4A (Fig. 1 A and B). Breast ultrasonography (US) demonstrated a hypoechoic oval mass measuring 26 × 23 × 16 mm with primarily circumscribed but partially microlobulated margins in the outer region of the right breast. The mass exhibited heterogeneous internal echotexture, posterior acoustic enhancement, and internal vascularity, and it was also categorized as BI-RADS 4A (Fig. 1 C). A vacuum assisted biopsy was performed, and histopathological examination revealed atypical ductal proliferation with mitoses and small glandular lumina against a fibrotic background. The glands were variably sized, with some containing mucinous material. IHC showed partial mosaic patterns of S100, CK5/6, E-cadherin, and smooth muscle actin (SMA), along with tumor cell expression of CK7, Bcl-2, and 34βE12. Nuclear p63 expression was heterogeneously observed in tumor cells, but it did not highlight myoepithelial cells around tumor nests. There was no expression of p40, ER, PR, HER2, c-Kit, or androgen receptors. The provisional diagnosis was an unusual ductal proliferation, but the possibility of a rare type of invasive breast carcinoma could not be excluded. The patient underwent a lumpectomy for definitive diagnosis. Macroscopically, the resected specimen revealed a 26-mm mass with distinct borders and heterogeneous internal features (Fig. 2 A). On low-power examination, the tumor was surrounded by a fibrous pseudocapsule with focally disrupted pushing margins (Fig. 2 B, C). Histologically, the tumor cells were arranged in various patterns, including solid, cribriform, glandular, and cord-like structures. The cord-like structures were predominantly located peripherally and showed stromal invasion. (Fig. 2 D, E). The neoplastic cells were uniform, with round nuclei, small but prominent nucleoli, and a roundish morphology. While no necrosis was observed, numerous mitotic figures were present, reaching 10 per 10 high-power fields (Fig. 2 F). No lymphovascular or perineural invasion was detected. The tumor was diagnosed as invasive breast carcinoma based on focal capsular destruction and stromal invasion. The area of disruption was located on the top of the tumor, which does not correspond to the typical site of needle biopsy. Moreover, no thermal degeneration or histological features suggestive of artifact were observed. The Nottingham histological grade was 2 ( 4 ). IHC findings were consistent with those of the initial biopsy, with additional expression of vimentin (Fig. 3 A-H). The final diagnosis was a PmA-like tumor of the breast with a pathological stage of T2N0M0 (stage IIA) ( 5 ). Due to a positive surgical margin in the initial excision biopsy, the patient underwent additional resection and sentinel lymph node biopsy. The final pathological assessment revealed no residual tumor in the breast and no metastasis in sentinel lymph nodes. The patient opted against adjuvant chemotherapy and radiotherapy. At 26 months of follow-up, there were no signs of recurrence. Discussion The breast can harbor neoplastic lesions with features resembling those of salivary glands. These tumors are classified under the “Rare and salivary gland-type tumors” category in the WHO Breast Tumour Classification, 5th edition ( 1 ). The present case exhibited diverse microscopic features, including solid, cribriform, tubule-forming, and scirrhous growth patterns with hyalinization and a mucus-like substrate. These features closely resemble those of polymorphous adenocarcinoma of the salivary glands (PmA-SG) ( 6 , 7 ). Furthermore, the IHC profile revealed positivity for CK7, S100, vimentin, Bcl-2, and p63, whereas p40, ER, PR, and HER2 were negative. Interestingly, SMA and high molecular weight CK, which are rarely expressed in PmA-SG, were observed in this case. However, their presence does not contradict the diagnosis ( 6 , 7 ). Unfortunately, molecular profiling of this tumor could not be performed. The differential diagnosis included adenoid cystic carcinoma (ACC), adenomyoepithelioma, secretory carcinoma, and mucoepidermoid carcinoma. The diagnosis of a PmA-like tumor of the breast was established based on its distinct morphological features and IHC profile, particularly the diffuse and strong co-expression of CK7 and Bcl-2. This tumor exhibited a fibrous pseudocapsule, reminiscent of encapsulated papillary carcinoma, which is typically staged as an in situ lesion. However, focal capsular destruction, stromal invasion, and the absence of myoepithelial cells (as indicated by negative p63 staining around tubular structures) suggested that the tumor was invasive. Notably, the previously reported four cases of PmA-like breast tumors lacked capsule-like structures and were more readily classified as invasive tumors ( 2 , 3 ). PmA-like tumors of the breast differ biologically from PmA-SG, despite their shared morphological and IHC features. A comparison of the IHC profiles of PmA-like breast tumors and PmA-SG is shown in Table 1 ( 8 – 12 ). Both expressed Bcl-2, S-100, and vimentin, while CK7 expression ranged from focal to diffuse. Unlike some PmA-SG cases, none of the PmA-like breast tumors, including our case, expressed c-Kit. Interestingly, SMA and p63 expression in our case differed from previous reports of PmA-like breast tumors but aligned with the profile of PmA-SG, which is typically positive for p63, negative for p40, and inconsistently expresses SMA ( 13 ). Given the similarities and differences between PmA in the breast and salivary glands, the term “PmA-like” for breast cases is advisable. Most PmA-like breast tumors express E-cadherin and are consistently negative for ER, PR, and HER2, indicating a triple-negative subtype. Our case, with heterogeneous weak to moderate positivity for p63 and SMA but negativity for p40, represents a notable variation from previously reported cases and suggests a closer resemblance to PmA-SG. Moreover, vimentin expression is uncommon in breast carcinoma and is often associated with basal-like and triple-negative subtypes ( 14 , 15 ). However, despite vimentin positivity, the IHC features in our case is more consistent with PmA-SG than basal-like breast carcinoma, which typically shows more aggressive behavior. PmA-SG is typically characterized by cellular uniformity, few mitoses, and a Ki-67 index below 5%, whereas this case demonstrated a relatively higher mitotic index and a Ki-67 index of 20% ( 8 , 9 ). PmA-SG is associated with mutations in PRKD1 , PRKD2 , or PRKD3 , but testing for these mutations in PmA-like breast tumors has been limited; only one case has been tested to date, with negative results ( 3 ). Imaging findings for PmA-like breast tumors have not been previously described. In this case, DBT and US demonstrated smooth margins and heterogeneous internal echoes, reflecting the pathological features of the fibrous pseudocapsule and internal heterogeneity of the mass. These findings are similar to the imaging characteristics of encapsulated papillary carcinoma, which typically exhibits circumscribed margins ( 16 ). However, this pattern may be specific to this case, which presented with a capsule-like structure. A clinicopathological comparison between our case and previously reported cases of PmA-like breast tumors is summarized in Table 1 . The patient in our case did not receive adjuvant therapy and remained recurrence-free after 26 months of follow-up. However, one reported case of a PmA-like breast tumor resulted in distant metastases and patient death ( 2 ). With only five cases reported to date, there is insufficient evidence to draw conclusions regarding the efficacy of adjuvant chemotherapy or radiotherapy and the overall prognosis of PmA-like breast tumors. Conclusion We report the first case of a PmA-like breast tumor with a fibrous pseudocapsule in Japan. Including this case, only five cases of PmA-like breast tumors have been reported to date, underscoring its rarity as a distinct entity in the breast. This case highlights the diagnostic challenges associated with vacuum assisted biopsy for such rare tumors. Further evaluation of additional cases is essential to better define the clinical and histopathological characteristics of PmA-like breast tumors. Declarations Author contributions: Y. H. and H.Y. managed the patient. The first draft of the manuscript was written by Y. H. and R.Y. Radiological findings were assessed by I.I. All the authors have read and approved the final manuscript. P. HT., F. MP. and R.Y. supervised. Acknowledgements: We thank Takuya Hara for pathological examination assistance. Statement of human rights: Ethical approval was not required because this report outlines a single case. Written informed consent was obtained from the patient for publication of this case report and the accompanying images. Conflicts of interest: The authors declare that there are no conflicts of interest in the publication of this report. References Foschini MP, Fox SB, Geyer FC, Marchiò C, McHugh JB, Nishimura R, Polymorphous D, White VA, Watanabe R, Cree IA, editors. World Health Organization Classification of Tumours of the Breast. 5th. ed. Lyon, France: IARC; 2019. Asioli S, Marucci G, Ficarra G, Stephens M, Foschini MP, Ellis IO, et al. Polymorphous adenocarcinoma of the breast. Report of three cases. Virchows Arch. 2006;448:29–34. 10.1007/s00428-005-0084-2 . Trihia HJ, Valavanis C, Novkovic N, Koutsodontis G, Petraki M, Efstathiou E. Polymorphous adenocarcinoma of the breast-an exceptionally rare entity: Clinicopathological description of a case and brief review. Breast J. 2020;26:261–64. 10.1111/tbj.13623 . Elston CW, Ellis IO. Pathological prognostic factors in breast cancer. Ⅰ. The value of histological grade in breast cancer: experience from a large study with long-term follow-up. Histopathology. 1991;19:403–10. 10.1111/j.1365-2559.1991.tb00229.x . Brierley JD, Gospodarowicz MK, Wittekind C, editors. TNM Classification of Malignant Tumours, 8th edition. Chichester, JohnWiley and Sons. Skálová A, Hyrcza MD, Leivo I. Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Salivary Glands. Head Neck Pathol. 2022;16(1):40–53. 10.1007/s12105-022-01420-1 . Epub 2022 Mar 21. PMID: 35312980; PMCID: PMC9018948. Vander Poorten V, Triantafyllou A, Skálová A, Stenman G, Bishop JA, Hauben E, Hunt JL, Hellquist H, Feys S, De Bree R, Mäkitie AA, Quer M, Strojan P, Guntinas-Lichius O, Rinaldo A, Ferlito A. Polymorphous adenocarcinoma of the salivary glands: reappraisal and update. Eur Arch Otorhinolaryngol. 2018;275(7):1681–95. Epub 2018 May 14. PMID: 29761209. Chatura KR. Polymorphous low grade adenocarcinoma. J Oral Maxillofac Pathol. 2015;19:77–82. 10.4103/0973-029X.157206 . Poorten VV, Triantafyllou A, Skálová A, Stenman G, Bishop JA, Hauben E, et al. Polymorphous adenocarcinoma of the salivary glands: reappraisal and update. Eur Arch Otorhinolaryngol. 2018;275:1681–95. 10.1007/s00405-018-4985-5 . Penner CR, Folpe AL, Budnick SD. C-kit expression distinguishes salivary gland adenoid cystic carcinoma from polymorphous low-grade adenocarcinoma. Mod Pathol. 2002;15:687–91. 10.1097/01.mp.0000018973.17736.f8 . Andreadis D, Epivatianos A, Poulopoulos A, Nomikos A, Papazoglou G, Antoniades D, et al. Detection of C-KIT (CD117) molecule in benign and malignant salivary gland tumours. Oral Oncol. 2006;42:57–65. 10.1016/j.oraloncology.2005.06.014 . Nonaka T, Takei H. Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis. Head Neck Pathol. 2022;16:980–90. 10.1007/s12105-022-01453-6 . Rooper L, Sharma R, Bishop JA. Polymorphous Low Grade Adenocarcinoma has a Consistent p63+/p402 Immunophenotype that Helps Distinguish it from Adenoid Cystic Carcinoma and Cellular Pleomorphic Adenoma. Head Neck Pathol. 2015;9:79–84. 10.1007/s12105-014-0554-4 . Korsching E, Packeisen J, Liedtke C, Hungermann D, Wülfing P, Diest PJ, et al. The origin of vimentin expression in invasive breast cancer: epithelial-mesenchymal transition, myoepithelial histogenesis or histogenesis from progenitor cells with bilinear differentiation potential? J Pathol. 2005;206:451–7. 10.1002/path.1797 . Chen Z, Fang Z, Ma J. Regulatory mechanisms and clinical significance of vimentin in breast cancer. Biomed Pharmacother. 2021;133:111068. 10.1016/j.biopha.2020.111068 . Bonnet SE, Carter GJ, Berg WA. Encapsulated Papillary Carcinoma of the Breast: Imaging Features with Histopathologic Correlation. J Breast Imaging. 2020;2:590–7. 10.1093/jbi/wbaa068 . Tables Table 1 is available in the Supplementary Files section. Supplementary Files ReTable1.docx Cite Share Download PDF Status: Published Journal Publication published 03 May, 2025 Read the published version in Breast Cancer → Version 1 posted Editorial decision: Accept 20 Apr, 2025 Reviewers agreed at journal 14 Apr, 2025 Reviewers invited by journal 14 Apr, 2025 Editor assigned by journal 14 Apr, 2025 First submitted to journal 13 Apr, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6075271","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":442963544,"identity":"74be98bb-5158-4482-ad40-2d4eb8c2d1f8","order_by":0,"name":"Yuki Hara","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/klEQVRIiWNgGAWjYPCCBB4GCSDF2GADIhsPkKIlDUwSpYUBquUwmItXizn78Ysff9SkyTBINz9g5t1x3m5t+2GgLTU20bi0WPbkFEvzHMvhYZA5ZsDMe+Z28rYziUAtx9JyG3BoMTiQkyDNwFYB9EsOAzNv2+1kswNALUAX4tZy/k3yzx//4FrOJZudf0hAy430YxK8bTkwLQfszG4QsuXGGzZr3r40HjagXw7ObUtOMLsBtCUBn1/Opz+++eNbsj2/dPPDB2/b7OzNzqc/fPChxganFgYGHgMwxQbEh3gYGBLBKhNwKgcB9gdwJuMPBgZ7vIpHwSgYBaNgRAIAnSVhlkuA+/kAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-7866-5606","institution":"Sasebo City General Hospital","correspondingAuthor":true,"prefix":"","firstName":"Yuki","middleName":"","lastName":"Hara","suffix":""},{"id":442963545,"identity":"2942864b-7f62-4371-be84-ca4e3f3727f4","order_by":1,"name":"Puay Hoon Tan","email":"","orcid":"","institution":"Luma Medical Centre, Royal Square Medical Centre","correspondingAuthor":false,"prefix":"","firstName":"Puay","middleName":"Hoon","lastName":"Tan","suffix":""},{"id":442963546,"identity":"ac6e0d0e-2713-4070-b103-52c7b6a39577","order_by":2,"name":"Foschini Maria Pia","email":"","orcid":"","institution":"Bellaria Hospital","correspondingAuthor":false,"prefix":"","firstName":"Foschini","middleName":"Maria","lastName":"Pia","suffix":""},{"id":442963547,"identity":"09cf11ca-e841-4fd8-b813-75ecfddf79b5","order_by":3,"name":"Hiroshi Yano","email":"","orcid":"","institution":"Sasebo City General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hiroshi","middleName":"","lastName":"Yano","suffix":""},{"id":442963548,"identity":"699ac395-5058-4d90-9713-5af4a00a62ab","order_by":4,"name":"Saki Sawada","email":"","orcid":"","institution":"Nagasaki University: Nagasaki Daigaku","correspondingAuthor":false,"prefix":"","firstName":"Saki","middleName":"","lastName":"Sawada","suffix":""},{"id":442963549,"identity":"420f41c6-ec64-468a-9977-6d456d70e07a","order_by":5,"name":"Hiroko Hayashi","email":"","orcid":"","institution":"Sasebo City General Hospital","correspondingAuthor":false,"prefix":"","firstName":"Hiroko","middleName":"","lastName":"Hayashi","suffix":""},{"id":442963550,"identity":"07cab8f6-8fd2-487a-bcc4-e44f549fbd73","order_by":6,"name":"Ichiro Isomoto","email":"","orcid":"","institution":"Saint Francis Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ichiro","middleName":"","lastName":"Isomoto","suffix":""},{"id":442963551,"identity":"6dbefdfa-478a-471b-9069-6add7e050c47","order_by":7,"name":"Rin Yamaguchi","email":"","orcid":"","institution":"Nagasaki University Hospital: Nagasaki Daigaku Byoin","correspondingAuthor":false,"prefix":"","firstName":"Rin","middleName":"","lastName":"Yamaguchi","suffix":""}],"badges":[],"createdAt":"2025-02-21 01:45:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6075271/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6075271/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s12282-025-01708-4","type":"published","date":"2025-05-03T15:57:07+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":80801968,"identity":"f6747ff5-d73a-4ee3-a436-33d4fca7bbd1","added_by":"auto","created_at":"2025-04-17 08:45:09","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":5713,"visible":true,"origin":"","legend":"\u003cp\u003e(A, B) Digital breast tomosynthesis (A: Medio-Lateral Oblique view, B: Cranio-Caudal view) shows the oval mass with mostly circumscribed but partially obscured margins in the middle-outer region of the right breast. (C) The lobulated oval mass with primarily circumscribed but partially microlobulated margins, internal heterogeneity and vascularity in the right breast on breast ultrasonography.\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-6075271/v1/4dd7657c459bc1f4c43e7eec.png"},{"id":80801114,"identity":"385bba04-7d64-433e-9763-0562da7c2964","added_by":"auto","created_at":"2025-04-17 08:37:10","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2867654,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Macroscopic examination revealed a whitish mass with distinct borders and heterogeneous internal features. (B, C) Hematoxylin and eosin (HE) staining (x0.25, x2) demonstrated proliferating atypical cells surrounded by a fibrous pseudocapsule. Focal disruption of the pseudocapsule and stromal invasion were observed. (D) HE staining (x20) showed tumor cells exhibiting a glandular growth pattern with secretion. (E) HE staining (x10) revealed solid cancer nests invading the hyalinized stroma with mucinous changes. (F) HE staining (x40) identified mitotic figures in some atypical epithelial cells (arrows).\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6075271/v1/7e20ba03aee059ff64036a28.jpeg"},{"id":80801970,"identity":"9fbb8b3c-ec8d-48ce-9ac7-656429866fa4","added_by":"auto","created_at":"2025-04-17 08:45:10","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3125256,"visible":true,"origin":"","legend":"\u003cp\u003eImmunohistochemical analysis revealed that tumor cells expressed p63, vimentin, S100, Bcl-2, cytokeratin (CK) 5/6, alpha-smooth muscle actin (SMA), CK7, and E-cadherin.\u003cbr\u003e\n(A) p63: heterogeneous weak to moderate positivity (x10), (B) vimentin: diffuse positivity (x10), (C) S100: heterogeneous positivity (x10), (D) Bcl-2: diffuse positivity (x20), (E) CK5/6: heterogeneous positivity (x10), (F) SMA: heterogeneous weak to moderate positivity (x20), (G) CK7: diffuse positivity (x10), (H) E-cadherin: heterogeneous positivity (x10).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6075271/v1/476c83e01cfc61c8ee19839b.jpeg"},{"id":81987767,"identity":"d453efa9-e54d-4b86-af01-546cc3a7ea6d","added_by":"auto","created_at":"2025-05-05 16:05:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6349543,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6075271/v1/4d7d0e96-003e-49c7-b888-18589539560a.pdf"},{"id":80801107,"identity":"c30522af-d7f7-4e95-a097-6e423d33f58d","added_by":"auto","created_at":"2025-04-17 08:37:09","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":20411,"visible":true,"origin":"","legend":"","description":"","filename":"ReTable1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6075271/v1/668682ad6aad9cd9bbd9c945.docx"}],"financialInterests":"","formattedTitle":"Polymorphous adenocarcinoma-like tumor of the breast: The first case report from Japan","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePolymorphous adenocarcinoma-like (PmA-like) tumor of the breast is an exceptionally rare neoplasm with histological features resembling salivary gland tumors. According to the World Health Organization (WHO), PmA of the breast is characterized histopathologically by a proliferation of monotonous neoplastic cells with architectural diversity. These cells are arranged in a variety of patterns, including large nests surrounded by cords and single files (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). To date, only four cases of PmA-like tumor of the breast have been reported in the literature (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). All previously documented cases exhibited a triple-negative phenotype, as they were negative for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Immunohistochemical (IHC) analyses demonstrated positivity for cytokeratin (CK) 7 and Bcl-2, with negativity for p63 and alpha-smooth muscle actin (SMA).\u003c/p\u003e \u003cp\u003eHerein, we present the first reported case in Japan of an invasive PmA-like tumor of the breast with a fibrous pseudocapsule. Uniquely, this case demonstrated heterogeneous weak to moderate immunoreactivity for p63 and SMA, alongside findings consistent with previously reported cases.\u003c/p\u003e"},{"header":"Case presentation","content":"\u003cp\u003eA 40-year-old premenopausal woman presented with a painful mass in her right breast that had appeared a few days prior. She had no significant medical or family history and had experienced one pregnancy and childbirth. Physical examination revealed no visible skin changes.\u003c/p\u003e \u003cp\u003eDigital breast tomosynthesis (DBT) identified a 26 mm high-density oval mass with predominantly circumscribed but partially obscured margins in the middle-outer region of the right breast. No calcifications or axillary lymphadenopathy were observed. The lesion was assigned a Breast Imaging Reporting and Data System (BI-RADS) score of 4A (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA and B). Breast ultrasonography (US) demonstrated a hypoechoic oval mass measuring 26 \u0026times; 23 \u0026times; 16 mm with primarily circumscribed but partially microlobulated margins in the outer region of the right breast. The mass exhibited heterogeneous internal echotexture, posterior acoustic enhancement, and internal vascularity, and it was also categorized as BI-RADS 4A (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003eA vacuum assisted biopsy was performed, and histopathological examination revealed atypical ductal proliferation with mitoses and small glandular lumina against a fibrotic background. The glands were variably sized, with some containing mucinous material. IHC showed partial mosaic patterns of S100, CK5/6, E-cadherin, and smooth muscle actin (SMA), along with tumor cell expression of CK7, Bcl-2, and 34βE12. Nuclear p63 expression was heterogeneously observed in tumor cells, but it did not highlight myoepithelial cells around tumor nests. There was no expression of p40, ER, PR, HER2, c-Kit, or androgen receptors.\u003c/p\u003e \u003cp\u003eThe provisional diagnosis was an unusual ductal proliferation, but the possibility of a rare type of invasive breast carcinoma could not be excluded. The patient underwent a lumpectomy for definitive diagnosis.\u003c/p\u003e \u003cp\u003eMacroscopically, the resected specimen revealed a 26-mm mass with distinct borders and heterogeneous internal features (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). On low-power examination, the tumor was surrounded by a fibrous pseudocapsule with focally disrupted pushing margins (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB, C). Histologically, the tumor cells were arranged in various patterns, including solid, cribriform, glandular, and cord-like structures. The cord-like structures were predominantly located peripherally and showed stromal invasion. (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD, E). The neoplastic cells were uniform, with round nuclei, small but prominent nucleoli, and a roundish morphology. While no necrosis was observed, numerous mitotic figures were present, reaching 10 per 10 high-power fields (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF). No lymphovascular or perineural invasion was detected.\u003c/p\u003e \u003cp\u003eThe tumor was diagnosed as invasive breast carcinoma based on focal capsular destruction and stromal invasion. The area of disruption was located on the top of the tumor, which does not correspond to the typical site of needle biopsy. Moreover, no thermal degeneration or histological features suggestive of artifact were observed. The Nottingham histological grade was 2 (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). IHC findings were consistent with those of the initial biopsy, with additional expression of vimentin (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA-H).\u003c/p\u003e \u003cp\u003eThe final diagnosis was a PmA-like tumor of the breast with a pathological stage of T2N0M0 (stage IIA) (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). Due to a positive surgical margin in the initial excision biopsy, the patient underwent additional resection and sentinel lymph node biopsy. The final pathological assessment revealed no residual tumor in the breast and no metastasis in sentinel lymph nodes.\u003c/p\u003e \u003cp\u003eThe patient opted against adjuvant chemotherapy and radiotherapy. At 26 months of follow-up, there were no signs of recurrence.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe breast can harbor neoplastic lesions with features resembling those of salivary glands. These tumors are classified under the \u0026ldquo;Rare and salivary gland-type tumors\u0026rdquo; category in the WHO Breast Tumour Classification, 5th edition (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e). The present case exhibited diverse microscopic features, including solid, cribriform, tubule-forming, and scirrhous growth patterns with hyalinization and a mucus-like substrate. These features closely resemble those of polymorphous adenocarcinoma of the salivary glands (PmA-SG) (\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e). Furthermore, the IHC profile revealed positivity for CK7, S100, vimentin, Bcl-2, and p63, whereas p40, ER, PR, and HER2 were negative. Interestingly, SMA and high molecular weight CK, which are rarely expressed in PmA-SG, were observed in this case. However, their presence does not contradict the diagnosis (\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e). Unfortunately, molecular profiling of this tumor could not be performed.\u003c/p\u003e\n\u003cp\u003eThe differential diagnosis included adenoid cystic carcinoma (ACC), adenomyoepithelioma, secretory carcinoma, and mucoepidermoid carcinoma. The diagnosis of a PmA-like tumor of the breast was established based on its distinct morphological features and IHC profile, particularly the diffuse and strong co-expression of CK7 and Bcl-2.\u003c/p\u003e\n\u003cp\u003eThis tumor exhibited a fibrous pseudocapsule, reminiscent of encapsulated papillary carcinoma, which is typically staged as an in situ lesion. However, focal capsular destruction, stromal invasion, and the absence of myoepithelial cells (as indicated by negative p63 staining around tubular structures) suggested that the tumor was invasive. Notably, the previously reported four cases of PmA-like breast tumors lacked capsule-like structures and were more readily classified as invasive tumors (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003ePmA-like tumors of the breast differ biologically from PmA-SG, despite their shared morphological and IHC features. A comparison of the IHC profiles of PmA-like breast tumors and PmA-SG is shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e (\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e12\u003c/span\u003e). Both expressed Bcl-2, S-100, and vimentin, while CK7 expression ranged from focal to diffuse. Unlike some PmA-SG cases, none of the PmA-like breast tumors, including our case, expressed c-Kit. Interestingly, SMA and p63 expression in our case differed from previous reports of PmA-like breast tumors but aligned with the profile of PmA-SG, which is typically positive for p63, negative for p40, and inconsistently expresses SMA (\u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e). Given the similarities and differences between PmA in the breast and salivary glands, the term \u0026ldquo;PmA-like\u0026rdquo; for breast cases is advisable.\u003c/p\u003e\n\u003cp\u003eMost PmA-like breast tumors express E-cadherin and are consistently negative for ER, PR, and HER2, indicating a triple-negative subtype. Our case, with heterogeneous weak to moderate positivity for p63 and SMA but negativity for p40, represents a notable variation from previously reported cases and suggests a closer resemblance to PmA-SG. Moreover, vimentin expression is uncommon in breast carcinoma and is often associated with basal-like and triple-negative subtypes (\u003cspan class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e15\u003c/span\u003e). However, despite vimentin positivity, the IHC features in our case is more consistent with PmA-SG than basal-like breast carcinoma, which typically shows more aggressive behavior. PmA-SG is typically characterized by cellular uniformity, few mitoses, and a Ki-67 index below 5%, whereas this case demonstrated a relatively higher mitotic index and a Ki-67 index of 20% (\u003cspan class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e). PmA-SG is associated with mutations in \u003cem\u003ePRKD1\u003c/em\u003e, \u003cem\u003ePRKD2\u003c/em\u003e, or \u003cem\u003ePRKD3\u003c/em\u003e, but testing for these mutations in PmA-like breast tumors has been limited; only one case has been tested to date, with negative results (\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003eImaging findings for PmA-like breast tumors have not been previously described. In this case, DBT and US demonstrated smooth margins and heterogeneous internal echoes, reflecting the pathological features of the fibrous pseudocapsule and internal heterogeneity of the mass. These findings are similar to the imaging characteristics of encapsulated papillary carcinoma, which typically exhibits circumscribed margins (\u003cspan class=\"CitationRef\"\u003e16\u003c/span\u003e). However, this pattern may be specific to this case, which presented with a capsule-like structure.\u003c/p\u003e\n\u003cp\u003eA clinicopathological comparison between our case and previously reported cases of PmA-like breast tumors is summarized in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. The patient in our case did not receive adjuvant therapy and remained recurrence-free after 26 months of follow-up. However, one reported case of a PmA-like breast tumor resulted in distant metastases and patient death (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e). With only five cases reported to date, there is insufficient evidence to draw conclusions regarding the efficacy of adjuvant chemotherapy or radiotherapy and the overall prognosis of PmA-like breast tumors.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWe report the first case of a PmA-like breast tumor with a fibrous pseudocapsule in Japan. Including this case, only five cases of PmA-like breast tumors have been reported to date, underscoring its rarity as a distinct entity in the breast. This case highlights the diagnostic challenges associated with vacuum assisted biopsy for such rare tumors. Further evaluation of additional cases is essential to better define the clinical and histopathological characteristics of PmA-like breast tumors.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eY. H. and H.Y. managed the patient. The first draft of the manuscript was written by Y. H. and R.Y. Radiological findings were assessed by I.I. All the authors have read and approved the final manuscript. P. HT., F. MP. and R.Y. supervised.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Takuya Hara for pathological examination assistance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatement of human rights:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthical approval was not required because this report outlines a single case.\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from the patient for publication of this case report and the accompanying images.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest in the publication of this report.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFoschini MP, Fox SB, Geyer FC, Marchi\u0026ograve; C, McHugh JB, Nishimura R, Polymorphous D, White VA, Watanabe R, Cree IA, editors. World Health Organization Classification of Tumours of the Breast. 5th. ed. Lyon, France: IARC; 2019.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAsioli S, Marucci G, Ficarra G, Stephens M, Foschini MP, Ellis IO, et al. Polymorphous adenocarcinoma of the breast. Report of three cases. Virchows Arch. 2006;448:29\u0026ndash;34. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s00428-005-0084-2\u003c/span\u003e\u003cspan address=\"10.1007/s00428-005-0084-2\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTrihia HJ, Valavanis C, Novkovic N, Koutsodontis G, Petraki M, Efstathiou E. Polymorphous adenocarcinoma of the breast-an exceptionally rare entity: Clinicopathological description of a case and brief review. 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Detection of C-KIT (CD117) molecule in benign and malignant salivary gland tumours. Oral Oncol. 2006;42:57\u0026ndash;65. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.oraloncology.2005.06.014\u003c/span\u003e\u003cspan address=\"10.1016/j.oraloncology.2005.06.014\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNonaka T, Takei H. Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis. Head Neck Pathol. 2022;16:980\u0026ndash;90. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s12105-022-01453-6\u003c/span\u003e\u003cspan address=\"10.1007/s12105-022-01453-6\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRooper L, Sharma R, Bishop JA. Polymorphous Low Grade Adenocarcinoma has a Consistent p63+/p402 Immunophenotype that Helps Distinguish it from Adenoid Cystic Carcinoma and Cellular Pleomorphic Adenoma. Head Neck Pathol. 2015;9:79\u0026ndash;84. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s12105-014-0554-4\u003c/span\u003e\u003cspan address=\"10.1007/s12105-014-0554-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKorsching E, Packeisen J, Liedtke C, Hungermann D, W\u0026uuml;lfing P, Diest PJ, et al. The origin of vimentin expression in invasive breast cancer: epithelial-mesenchymal transition, myoepithelial histogenesis or histogenesis from progenitor cells with bilinear differentiation potential? J Pathol. 2005;206:451\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1002/path.1797\u003c/span\u003e\u003cspan address=\"10.1002/path.1797\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen Z, Fang Z, Ma J. Regulatory mechanisms and clinical significance of vimentin in breast cancer. Biomed Pharmacother. 2021;133:111068. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biopha.2020.111068\u003c/span\u003e\u003cspan address=\"10.1016/j.biopha.2020.111068\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBonnet SE, Carter GJ, Berg WA. Encapsulated Papillary Carcinoma of the Breast: Imaging Features with Histopathologic Correlation. J Breast Imaging. 2020;2:590\u0026ndash;7. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1093/jbi/wbaa068\u003c/span\u003e\u003cspan address=\"10.1093/jbi/wbaa068\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTable 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"breast-cancer","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"brca","sideBox":"Learn more about [Breast Cancer](http://link.springer.com/journal/12282)","snPcode":"12282","submissionUrl":"https://www.editorialmanager.com/brca/default2.aspx","title":"Breast Cancer","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Breast, polymorphous adenocarcinoma, rare tumor, salivary gland","lastPublishedDoi":"10.21203/rs.3.rs-6075271/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6075271/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003ePolymorphous adenocarcinoma-like (PmA-like) tumor of the breast is a rare salivary gland-like neoplasm, with few cases reported globally. We present the first case of a PmA-like tumor with a fibrous pseudocapsule from Japan, including radiological findings.\u003c/p\u003e \u003cp\u003eA 40-year-old premenopausal woman presented with a painful mass in the right breast. Mammography revealed a high-density oval mass with predominantly circumscribed margins, while ultrasonography showed a hypoechoic oval mass with heterogeneous internal echoes and vascularity. Both imaging modalities suggested malignancy, prompting a vacuum assisted biopsy. Histopathological evaluation demonstrated diverse growth patterns and positivity for cytokeratin (CK) 7 and Bcl-2. Initially diagnosed as an unusual ductal proliferation, malignancy could not be excluded, leading to lumpectomy.\u003c/p\u003e \u003cp\u003eThe resected tumor measured 26 mm, exhibited a fibrous pseudocapsule with focal disruption, and showed varied histological patterns, including solid, cribriform, glandular, and cord-like structures. Immunohistochemistry revealed expression of CK7, S100, vimentin, CK5/6, E-cadherin, Bcl-2, p63, and smooth muscle actin (SMA), with no expression of p40, estrogen receptor, progesterone receptor, HER2, c-Kit, or androgen receptor. These findings, including penetration beyond the capsule, supported the diagnosis of an invasive PmA-like tumor of the breast.\u003c/p\u003e \u003cp\u003eFollowing surgery, the patient underwent additional resection and sentinel lymph node biopsy due to a positive margin. No residual tumor or nodal metastases were found. The patient declined adjuvant therapy and remains recurrence-free after 26 months of follow-up.\u003c/p\u003e \u003cp\u003ePmA-like tumors of the breast present diagnostic challenges due to their rarity and diverse histopathological features. Further studies are necessary to characterize their clinical behavior and guide management strategies.\u003c/p\u003e","manuscriptTitle":"Polymorphous adenocarcinoma-like tumor of the breast: The first case report from Japan","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-17 08:37:05","doi":"10.21203/rs.3.rs-6075271/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accept","date":"2025-04-21T01:49:01+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-04-15T02:37:03+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-04-15T01:15:57+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-15T01:11:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"Breast Cancer","date":"2025-04-13T06:17:37+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"breast-cancer","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"brca","sideBox":"Learn more about [Breast Cancer](http://link.springer.com/journal/12282)","snPcode":"12282","submissionUrl":"https://www.editorialmanager.com/brca/default2.aspx","title":"Breast Cancer","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b2d1a742-a940-4bd4-939d-3be6674af3a8","owner":[],"postedDate":"April 17th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-05-05T16:01:17+00:00","versionOfRecord":{"articleIdentity":"rs-6075271","link":"https://doi.org/10.1007/s12282-025-01708-4","journal":{"identity":"breast-cancer","isVorOnly":false,"title":"Breast Cancer"},"publishedOn":"2025-05-03 15:57:07","publishedOnDateReadable":"May 3rd, 2025"},"versionCreatedAt":"2025-04-17 08:37:05","video":"","vorDoi":"10.1007/s12282-025-01708-4","vorDoiUrl":"https://doi.org/10.1007/s12282-025-01708-4","workflowStages":[]},"version":"v1","identity":"rs-6075271","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6075271","identity":"rs-6075271","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}