Immunoreactivity for cytokeratin and epithelial membrane antigen in leiomyosarcoma

Thirty-three leiomyosarcomas (LMS), which were verified by electron microscopy and by desmin and muscle actin immunoreactivity, were immunohistochemically evaluated for the presence of cytokeratin and epithelial membrane antigen (EMA) with monoclonal antibodies. None of the tumors showed any epithelial component by structure; all were homogeneous spindle cell neoplasms. Cytokeratin immunoreactivity was found in 14 of 33, and EMA in 20 of 33 LMS, usually in a large number of tumor cells. One case was confirmed as cytokeratin-positive in frozen sections with four different monoclonal antibodies. These results show that immunoreactivity for epithelial markers can be present in pure smooth-muscle sarcomas. Thus, such immunoreactivity cannot be regarded as a specific feature of carcinomas, synovial sarcoma, or epithelioid sarcoma, which are already known to be cytokeratin- and EMA-positive.