{"paper_id":"ada011d6-16d5-4668-8579-f43fe46eeabc","body_text":"Abstract\nA 63-year-old woman presented with a clinically malignant mass. Core biopsy showed features resembling endometriosis. The glands were GATA3 and oestrogen receptor positive consistent with mammary origin and had no myoepithelial layer. The excision also showed a fibroepithelial component with stromal overgrowth, frequent mitoses and invasive margin consistent with a malignant phyllodes tumour. KMT2D and SETD2 mutations were present in both the conventional phyllodes tumour and endometriosis-like areas and are also described in endometriosis raising interesting questions about these lesions. This unusual pattern is a potential diagnostic pitfall, so it is helpful to be aware of it.\nData availability\nNot appropriate.\nCode availability\nNot appropriate.\nReferences\nMd Nasir ND, Ng CCY, Rajasegaran V, Wong SF, Liu W, Ng GXP, Lee JY, Guan P, Lim JQ, Thike AA, Koh VCY, Loke BN, Chang KTE, Gudi MA, Lian DWQ, Madhukumar P, Tan BKT, Tan VKM, Wong CY, Yong WS, Ho GH, Ong KW, International Fibroepithelial Consortium, Tan P, Teh BT, Tan PH, Rahman NA, Nahar Begum SMK, Cheah PL, Chen CJ, dela Fuente E, Han A, Harada O, Kanomata N, Lee CS, Han Lee JY, Kamal M, Nishimura R, Ohi Y, Sawyer EJ, Teoh KH, Tsang AKH, Tsang JYS, Tse GMK, Yamaguchi R (2019) Genomic characterisation of breast fibroepithelial lesions in an international cohort. J Pathol 249:447–460\nChia Y, Thike AA, Cheok PY, Yong-Zheng Chong L, Man-Kit Tse G, Tan PH (2012) Stromal keratin expression in phyllodes tumours of the breast: a comparison with other spindle cell breast lesions. J Clin Pathol 65:339–347\nMoloshok AA, Ivanko A (1984) Endometriosis of the breast (case report). Vopr Onkol 30:88–89\nLi X, Zhang Y, Zhao L, Wang L, Wu Z, Mei Q, Nie J, Li X, Li Y, Fu X, Wang X, Meng Y, Han W (2014) Whole-exome sequencing of endometriosis identifies frequent alterations in genes involved in cell adhesion and chromatin-remodeling complexes. Hum Mol Genet 23:6008–6021\nTan WJ, Chan JY, Thike AA, Lim JCT, Md Nasir ND, Tan JSY, Koh VCY, Lim WK, Tan J, Ng CCY, Rajasegaran V, Nagarajan S, Bay BH, Teh BT, Tan PH (2016) MED12 protein expression in breast fibroepithelial lesions: correlation with mutation status and oestrogen receptor expression. J Clin Pathol 69:858–865\nGuo SW (2020) Cancer-associated mutations in endometriosis: shedding light on the pathogenesis and pathophysiology. Hum Reprod Update 26:423–449\nPareja F, Geyer FC, Kumar R, Selenica P, Piscuoglio S, Ng CKY, Burke KA, Edelweiss M, Murray MP, Brogi E, Weigelt B, Reis-Filho JS (2017) Phyllodes tumors with and without fibroadenoma-like areas display distinct genomic features and may evolve through distinct pathways. NPJ Breast Cancer 3:40\nAuthor information\nAuthors and Affiliations\nContributions\nAHSL, UZ, RA and PHT reviewed the pathology and wrote the pathology section. MJH wrote the clinical section. NDMN, CCYN and BTT did the molecular analysis and with PHT wrote the molecular section.\nCorresponding author\nEthics declarations\nEthics approval\nNot appropriate.\nConsent to participate\nNot appropriate.\nConsent for publication\nWe thank the patient for her consent to genetic testing.\nConflict of interest\nBTT and PHT jointly hold patent applications for PCT/SG2015/050107 (Breast fibroadenoma susceptibility mutations and use thereof) and PCT/SG2015/050368 (method and kit for pathologic grading of breast neoplasms).\nAdditional information\nPublisher’s note\nSpringer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.\nRights and permissions\nAbout this article\nCite this article\nLee, A.H.S., Zanetto, U., Awasthi, R. et al. Malignant phyllodes tumour of the breast mimicking endometriosis. Virchows Arch 479, 1051–1053 (2021). https://doi.org/10.1007/s00428-021-03086-6\nReceived:\nRevised:\nAccepted:\nPublished:\nVersion of record:\nIssue date:\nDOI: https://doi.org/10.1007/s00428-021-03086-6","source_license":"CC0","license_restricted":false}