In fact, it has been shown cytogenetically by several groups that the fusion member derived from the X chromosome (“der(X)” or SSX2) rather than the derivative member from chromosome 18 (“der(18)” or SS18) is important for maintaining proliferation and that der18 can be lost during the course of SS progression suggesting that the expression of the C-terminal portion of SSX may be the dominant event leading to tumor progression [16, 17, 19, 23, 24]. The gene discussed is SS18; the disease is synovial sarcoma.