SYT–SSXGene Fusion as a Determinant of Morphology and Prognosis in Synovial Sarcoma

Synovial sarcomas account for up to 10 percent of soft-tissue sarcomas and include two major histologic subtypes, biphasic and monophasic, defined respectively by the presence and absence of glandular epithelial differentiation in a background of spindle tumor cells. A characteristic SYT–SSX fusion gene resulting from the chromosomal translocation t(X;18)(p11;q11) is detectable in almost all synovial sarcomas. The translocation fuses the SYT gene from chromosome 18 to either of two highly homologous genes at Xp11, SSX1 or SSX2. SYT–SSX1 and SYT–SSX2 are thought to function as aberrant transcriptional regulators. We attempted to determine the influence of the two alternative forms of the SYT–SSX fusion gene on tumor morphology and clinical outcome in patients with this sarcoma.