We are trying to exploit some of the proteins made by synovial sarcoma (cancer-germ cell or cancer-testis antigens) as targets for the immune system. Specifically, we are investigating if immune-based therapy with anti-CTLA4 antibody once every 4 weeks for three treatments will activate the immune system enough to attack recurrent synovial sarcoma. In this study the tumor itself serves as the "vaccine" or source of protein, as we try to activate tumor-fighting T cells with the anti-CTLA4.