Monosomy 22 and partial loss of INI1 expression in a biphasic synovial sarcoma with an Ewing sarcoma-like poorly differentiated component: Report of a case.

Poorly differentiated synovial sarcoma (PDSS) is a less common subtype of synovial sarcoma (SS) associated with a poor prognosis. We present a case of a SS with a poorly differentiated component that resembles Ewing sarcoma (ES). Initial immunohistochemical staining revealed a characteristic and strong expression of transducin-like enhancer of split 1 (TLE1) and weak to absent expression of integrase integrator 1 (INI1) staining.