Metastatic Monophasic Synovial Sarcoma: A challenging Diagnosis on Fine Needle Aspiration with Broad Differential Diagnosis

Synovial sarcomas (SS) are rare soft tissue sarcomas that usually arise near large extremity joints. SS may pose difficult diagnostic challenges on cytology when encountered as a monophasic variant. We report a 27-year-old woman diagnosed with metastatic monophasic synovial sarcoma by a CT-scan guided fine needle aspiration (FNA) biopsy of a left lower lung lobe nodule. We reviewed the literature on the epidemiologic, cytohistological spectrum, immunophenotypic, and the molecular findings and discussed the differential diagnosis for this rare entity.