Sarcomatoid carcinoma of the colon. Report of the second case with immunohistochemical study.

Sarcomatoid Carcinomas are rare tumors composed of mixed malignant epithelial and mesenchymal cells. Only one case is reported in the colon, up to date. We describe the second case in an 86-year-old woman. The tumor, replacing the intestinal wall, consisted of carcinomatous and sarcomatous areas. The former was composed of differentiated superficial adenocarcinoma and of infiltrating epithelioid undifferentiated solid portion. The latter was mostly composed of undifferentiated spindle cells with focal chondrosarcomatous and pleomorphic anaplastic areas. A strong Cytocheratin (CK) and Epithelial Membrane Antigen (EMA) immunoreactivity (IR) with focal CA 125 positivity was detected in differentiated adenocarcinomatous areas. Solid carcinoma-like areas coexpressed CK and Vimentin (VIM). The sarcomatous spindle-cell component of the tumor was largely VIM positive, with focal CK IR. Both polyclonal and monoclonal antibodies for Carcino-Embryonic Antigen (CEA) did not display any reaction.