Malignant peripheral nerve sheath tumors with t(X;18). A pathologic and molecular genetic study (vol 13, pg 1336, 2000)

Spindle cell sarcomas often present the surgical pathologist with a conside rable diagnostic challenge. Malignant peripheral nerve sheath tumor, leiomy osarcoma, fibrosarcoma, and monophasic synovial sarcoma may all appear simi lar histologically. The application of ancillary diagnostic modalities, suc h as immunohistochemistry and electron microscopy, may be helpful in the di fferentiation of these tumors, but in cases in which these adjunctive techn iques fail to demonstrate any more definitive evidence of differentiation, tumor categorization may remain difficult. Cytogenetic and molecular geneti c characterization of tumors have provided the basis for the application of molecular assays as the newest components of the diagnostic armamentarium. Because the chromosomal translocation t(X;18) has been observed repeatedly in many synovial sarcomas, it has been heralded as a diagnostic hallmark o f synovial sarcoma To formally test the specificity of this translocation f or the diagnosis of synovial sarcoma, RNA extracted from formalin-fixed, pa raffin-embedded tissue from a variety of soft tissue and spindle cell tumor s was evaluated for the presence of t(X;18) by reverse transcriptase-polyme rase chain reaction. Although 85% of the synovial sarcomas studied demonstr ated t(X;18), 75% of the malignant peripheral nerve sheath tumors in our co hort also demonstrated this translocation. We conclude that the translocati on t(X;18) is not specific to synovial sarcoma and discuss the implications of the demonstration of t(X;18) in a majority of malignant peripheral nerv e sheath tumors.