Metaplastic carcinoma with squamous cell component

Purpose To study the clinicopathological and immunohistochemical characteristics of metaplastic carcinoma with squamous cell component (MCSC) of the breast. Methods Clinical information and pathological changes of 20 cases were reviewed and summarized. Results This series consisted of squamous cell carcinoma(SCC) in 6 patients, adenosquamous carcinoma(ASC) in 13 and carcinosarcoma in 1. The mean age of all patients was 52.4 years old and the tumors usually presented as painless mass. Metastasis was observed in 60% of the SCC cases and 66.7% of the ASC cases with axillary lymph node dissection. Grossly 45% of the cases showed cystic change. Microscopically, phenotypes of SCC included keratinizing, acantholytic, mixed keratinizing and acantholytic, mixed keratinizing and spindle cell types. The squamous elements of ASC were exclusively keratinizing type. The adenocarcinoma in ASC presented as invasive ductal carcinoma and mucinous carcinoma coexisted only in one case. The carcinosarcoma case contained SCC, adenocarcinoma and chondrosarcoma. All SCCs performed immunohistochemical stain demonstrated staining for CK34βE12, CK5/6, CK14, p63 but negative for ER and PR. Adenocarcinoma showed focal positive for CK34βE12,CK14 and CK5/6 in 5, 1 and 1 cases respectively. CK8 positive was observed in all adenocarcinoma, only one SCC presented focal positive. SMA was negative in both adenocarcinoma and SCC of all cases. Conclusions ASC is the most common subtype of MCSC and cystic change is one of the pathologic features, while the phenotypes and differentiation of SCC varied. A panel of CK14, p63 and CK8 may be useful in the diagnosis of SCC. Studies with consistent criterions and sufficient cases should give more useful clinicopathological information.