Small-cell variant of synovial sarcoma: Fine-needle aspiration with ancillary features and potential diagnostic pitfalls

We report a small-cell variant of synovial sarcoma examined by fine-needle aspiration (FNA) biopsy. The patient is a 23-yr-old female who had a synovi al sarcoma involving the left infratemporal region, diagnosed at 7 yr of ag e, followed by a metastatic lesion involving the lung and chest wall 16 yr later. The chest wall metastases was sampled by FNA biopsy. The aspirate co nsisted of numerous, small, round cells with very high nuclear-to-cytoplasm ic ratios. The cytomorphologic features could potentially be confused with other pediatric small round cell tumors. Ancillary studies demonstrated pos itive staining of the neoplastic cells for cytokeratin, epithelial membrane antigen (EMA), and CD99. The differential diagnosis of other small round c ell tumors that may be mistaken for the small-cell variant of synovial sarc oma are presented. We believe that this is the first FNA report detailing t he cytologic and ancillary features of the small-cell variant of synovial s arcoma. Diagn. Cytopathol. 2000;23:118-123. (C) 2000 Wiley-Liss, Inc.