Cytological findings of monophasic synovial sarcoma presenting as a lung mass: report of a case and review of the literature

Synovial sarcomas are rare malignant mesenchymal tumors that can arise from any anatomic site. Although they are often located at the paraarticular region of the extremities, the incidence of synovial sarcomas in the lungs is rare, with only a few cytology case reports to date. We report a case of synovial sarcoma presenting as a lung mass diagnosed on fine-needle aspiration (FNA) cytology. The patient is a 38-year-old chronic smoker who presented with cough, worsening dyspnea, and weight loss. Computerized tomography of his chest revealed an 8-cm left lower lobe pleural-based mass. An FNA of the lung mass showed cellular smears composed of monotonous population of singly scattered to sheets of bland spindle cells with elongated nuclei, fine chromatin pattern, and scant to moderate amount of delicate cytoplasm. Immunohistochemical stains performed on the cell block showed that the tumor cells were positive for calretinin and focally positive for pancytokeratin, CAM5.2, and smooth muscle myosin heavy chain. The tumor cells were negative for S-100, podoplanin, and CD34. Fluorescence in situ hybridization performed on the cell block demonstrated the presence of SYT (18q11) translocation, supporting the diagnosis of synovial sarcoma.