In conclusion, a panel of SOX-2, PAX-7, INI-1 and NKX3.1 immunohistochemical markers (combined with classical markers, such as TLE-1, CK-pan, EMA, CD99 and BCL-2) can be used as an ancillary tool for the differential diagnosis of SS. The gene discussed is SOX2; the disease is synovial sarcoma.