The basis for this striking heterogeneity in CT antigen expression is unknown. Two neoplastic lesions, seminomas and synovial sarcomas, are exceptions to this pattern of heterogeneous antigen expression. No association of mAb 57B immunostaining with the composition of the lymphocytic infiltrate or the apoptotic index could be shown. Synovial sarcomas are the other tumor type showing a high frequency of CT antigen expression and a homogeneous pattern of CT immunoreactivity. Based on our initial observation of extensive mAb 57B immunoreactivity in synovial sarcomas, a larger number of synovial sarcomas were immunohistochemically analyzed for CT antigen expression.
Synovial sarcomas are high-grade tumors, which are often associated with a poor prognosis.
The gene on chromosome X which is involved in the translocation is SSX, and a family of five SSX genes have been identified, with SSX1 and SSX2 being most commonly involved in the translocations observed in synovial sarcomas. MA454 showed little or no reactivity. CT antigen expression was found in both monophasic and biphasic synovial sarcomas and in both SSX1 and SSX2 translocation types. Serological reagents generated to additional CT antigens are being developed, and studies are under way to determine the temporal sequence of different CT antigen expression in germ cell development and in tumor progression.