The genetic hallmark of synovial sarcoma is the chromosomal translocation t(X;18)(p11;q11), which leads to a fusion of SS18 (SYT), which encodes a SWI–SNF complex component, to one of the homologues SSX genes (SSX1, SSX2, rarely SSX4), which encodes instead a transcriptional repressor [188,189]. This evidence concerns the gene SSX2 and synovial sarcoma.