Synovial Sarcoma With Myoid Differentiation

We describe a case of intraabdominal monophasic synovial sarcoma that immunohistochemically showed strong expression of smooth muscle actin and calponin but only very scanty cytokeratin, and which showed morphologic and immunohistochemical overlap with other spindle cell neoplasms that can arise at this site, such as gastrointestinal stromal tumor and myofibrosarcoma. As correct diagnosis is of clinical and prognostic importance, surgical pathologists should be aware of the potential for synovial sarcoma to occur at a variety of anatomic sites and of its spectrum of immunoreactivity. Synovial sarcoma should be in the differential diagnosis of spindle cell neoplasms with myoid differentiation that do not fall into any definite tumor category, for which there should be a relatively low threshold for performing fluorescence in situ hybridization or reverse transcription-polymerase chain reaction to assess for the specific SS18 gene rearrangement or SS18-SSX fusion transcripts, which remain the diagnostic gold standard.
Source: International Journal of Surgical Pathology - Category: Pathology Authors: Tags: Pitfalls in Pathology Source Type: research