SSX4 and synovial sarcoma: The majority of cases of synovial sarcoma contain a t(X;18)(p11.2;q11.2) translocation that results in the fusion of the chromosome 18 gene SYT to three closely related genes SSX1, SSX2 and SSX4 on the X chromosome (Clark et al, 1994; Crew et al, 1995; Skytting et al, 1999).