The main cytogenetic event is a balanced chromosomal translocation t(X;18)(p11.2;q11.2) [2–4], resulting in fusion of the synovial sarcoma translocation, chromosome 18 (SS18) gene, encoding one member of the switch/sucrose-non-fermentable (SWI/SNF) complex, with one of the synovial sarcoma, X-breakpoint 1, 2, or 4 (SSX1, SSX2, or SSX4) genes, which encode transcriptional repressors [5, 6]. Here, SS18 is linked to synovial sarcoma.