Monophasic mesenchymal synovial sarcoma: its identification by tissue culture

Tissue cultures from a series of spindle cell soft tissue sarcomas allowed th identification of five cases in which the neoplastic cells grew as polygonal elements, forming plaques in the same way as epithelial tumors. The similarity of this behavior in vitro to that of normal pleura and synovium, and to monophasic malignant pleural mesothelioma, allowed these tumors to be classified as monophasic synovial sarcomas. None of the five tumors showed specific light-optical features, being composed of fusiform cells with a tendency to form slits in two cases. No true epithelial differentiation was found. The topographic distribution and the response to therapy of the neoplasms were also similar to that found in the usual biphasic tumors.