Primary monophasic spindle cell synovial sarcoma of the lung

Primary pulmonary synovial sarcoma (PPSS) is an exceptionally rare malignancy representing < 0.5% of all primary lung tumors. The monophasic (spindle cell) variant poses significant diagnostic challenges due to its histological overlap with other spindle cell neoplasms of the lung. We report a case of a 24-year-old male deep-sea diver who presented with an acute onset of right-sided pleuritic chest pain and fever. Imaging revealed a large right lower lobe mass initially suspected to be hydatid disease. Following thoracotomy and lobectomy, the diagnosis of monophasic spindle cell synovial sarcoma was confirmed on histopathology and immunohistochemistry. The patient remains disease-free 1 year post-surgery. To conclude, primary synovial sarcoma of the lung should be considered in the differential diagnosis of large peripheral lung masses in young patients. Complete surgical resection remains the mainstay of treatment. Accurate diagnosis relies on immunohistochemistry and molecular confirmation.