Nealy all synovial sarcomas (over 90%) have been identified with a chromosomal translocation between SYT and SSX genes (Appendix Fig. S1) (Ladanyi et al, 2002), resulting in a fusion mutation of SYT to SSXs gene (including SSX1, SSX2, and SSX4). The gene discussed is SSX4; the disease is synovial sarcoma.