Breast Carcinosarcoma: The Report of a Unique Case Including Fibrosarcoma and Metaplasia of Squamous Carcinoma with Adenocarcinoma; a Case Report and the Literature Review

Introduction: Breast carcinosarcoma is an extremely rare breast tumor comprising two distinct components, a carcinomatous component and a non-epithelial component of mesenchymal origin. It is a subtype of metaplastic carcinoma with a difficult preoperative diagnosis. Case Presentation:We present the case of a 68-year-old postmenopausalwomanwith squamous metaplasia coexisting with adenocarcinoma in the epithelialcomponentof a breast carcinosarcoma. She has been admitted in Department of Breast Surgery, The First Hospital of Jilin University, Changchun, China, in 2017, with a left breast mass. Preoperative assessment and histopathological examination of biopsy samples did not confirm the diagnosis of breast carcinosarcoma. The evaluation of tissue removed during surgery showed three components: high-grade fibrosarcoma (70%), squamous cell carcinoma (25%), and adenocarcinoma (5%), which were consistent with the diagnosis of breast carcinosarcoma. Immunohistochemistry showed that the epithelial component was positive for cytokeratin (CK) 5/6, CK7, CK-pan, and P40, and the sarcomatous component was positive for vimentin and smooth muscle actin (SMA). The estrogen and progesterone receptors (ER, PR) were negative but HER-2/neu was positive (2+) in adenocarcinoma. Conclusions: Case studies describing the clinical characteristics, diagnosis, and treatment of breast carcinosarcoma are required to raise the awareness of the heterogeneous nature of this tumor among clinicians. Large prospective studies should be conducted to identify the most beneficial therapeutic protocol.