SSX4 and synovial sarcoma: Almost all the synovial sarcomas carry chromosomal translocation, t (X,18; p11, q11), resulting in the fusion onco-protein SS18-SSX in which C terminus of SSX gene family (most SSX1, less SSX2 and rarely SSX4) in X chromosome replaced the 8 C-terminal amino acids of SS18 protein encoded by chromosome 18 [16, 17] (Fig. 1a).