[Electron microscopic diagnosis of human synovial tumors]

The present study was aimed at the analysis of the ultrastructure of synovial tissue tumors and the determination of a set of signs of synovial differentiation for electron microscopic diagnosis of these neoplasias. Three benign giant cell synoviomas and 10 synovial sarcomas of different structures were studied. The results showed both benign and malignant synoviomas to have similar signs of synovial differentiation: cellular (signs of A- and B-cells of normal synovial membrane) and tissue signs (specific intercellular cavities). In benign synoviomas cellular signs are more marked, in malignant tumors tissue signs are more manifest but the detection of histioid and epithelioid components in the latter at the electron microscopic level has no principal significance. A hypothesis that A- and B-cells in synovial tumors and normal synovial membrane represent the same cellular form (synoviocyte) in different functional stages is discussed.