Synovial sarcoma of the abdominal wall. Light microscopic, histochemical and electron microscopic investigations.

A synovial sarcoma of the abdominal wall in a 56-year old woman showed the typical features of this tumor type. Histologically a characteristic biphasic cellular pattern with epithelium-like cell complexes and sarcomatous spindle cell areas was found. The histochemical examination revealed that tumor cells synthesize glycoproteins and weakly acid glycosaminoglycans (mainly hyaluronic acid). Electron microscopically the tumor cells in epithelium-like cell islets were sometimes arranged in gland-like formations with microvilli at the luminal side, specialized intercellular junctions and a peripheral basement membrane-like condensation of the ground substance. There was no fundamental cytological difference between cells of epithelium-like and spindle cell areas. Generally the tumor cells imitated cells of the synovial membrane and we found no evidence for origin from cells of the nerve sheath. Because of the submicroscopic relationship and histochemical similarities of synovial sarcomas and mesotheliomas we suggest that they should be united in a group of sarcomas with possible biphasic cellular pattern, while preserving their clinicopathologic definition.