Aspiration cytology of biphasic and monophasic synovial sarcoma. A report of two cases.

Two cases of synovial sarcoma diagnosed by aspiration cytology are described. A 15-year-old, athletic female presented with a tender midthigh mass clinically thought to be a hematoma. Aspiration cytology revealed numerous clusters of spindle cells admixed with small groups of epithelial cells. Cytokeratin and vimentin stains were positive in the epithelial and spindle components, respectively. Resection of the mass revealed a biphasic synovial sarcoma. Second, a 53-year-old male presented with a recurrent soft tissue mass 10 years after synovial sarcoma of the knee had been resected. Aspiration cytology revealed neoplastic spindle cells. Cytokeratin and vimentin preparations showed focal positivity. Resection revealed a predominantly monophasic synovial sarcoma. These cases demonstrate the utility of aspiration cytology in diagnosing both unsuspected and recurrent synovial sarcoma.