An Unusual Diagnosis of an Anterior Mediastinal Mass: A Case Report

Abstract Introduction: Primary thoracic synovial sarcoma is an exceptionally rare malignant tumor that resembles soft tissue synovial sarcoma histologically and genetically, but arises in the lung without evidence of extrapulmonary origin. Tumour biopsy, immunostaining and histologic analysis can assist in determining the kind of tumour. Case report: We report the case of a 57-year-old male with a 16 Pack-year smoking history, currently quit, presenting with progressive dyspnea and chest pain. Chest CT revealed an anterior mediastinal tissue partially calcified mass invading the pericardium and with the presence of intra cardiac thrombus. The histopathological features were suggestive of a rare type of lung malignancy. For further diagnosis regarding type of malignancy, immunohistochemical staining of the lesion was done with the help of specific immunological markers, which confirmed the diagnosis of monophasic pulmonary sarcoma. Molecular analysis confirmed a diagnosis of monophasic synovial sarcoma with SYT-SSX1 gene fusion. The patient underwent chemotherapy. Conclusion: Thoracic Synovial Sarcoma is a diagnostic challenge due to its rarity and nonspecific clinical presentation. Molecular confirmation is essential. Complete surgical excision remains the mainstay of treatment. Keywords: Primary mediastinal synovial sarcoma; Lung tumor; Cardiac thrombus; SYT-SSX; Chemotherapy