Cardiac synovial sarcoma masquerading as effusive constrictive pericarditis

Primary cardiac synovial sarcoma is a rare entity, arising from the pericardium or the chambers of the heart. It presents in the 4^th decade of life with a striking male predisposition. We describe an unusual case of a 22-year-old female who presented with complaints of dyspnoea on exertion, palpitations, and chest pain. Trans-thoracic echocardiography was suggestive of a cystic pericardial mass with pericardial effusion anterior and lateral to the right ventricle. Computed tomography scan (CT scan) revealed thick-walled predominantly cystic lesion over the left ventricle with gross pericardial effusion with internal septations. These findings were suggestive of an infected pericardial cyst. Upon surgery, an adherent mass in the pericardial cavity was found which was not separable from the right heart structures, the great vessels, and the left ventricle. Biopsy was taken, histopathology was suggestive of spindle cell neoplasm, and an immunohistochemistry analysis revealed Transducin-like enhancer of split 1 (TLE 1)-positive malignant spindle cell tumour likely synovial sarcoma. After surgery, the patient received serial adjuvant chemo-radiation therapy. The synovial sarcoma masqueraded as effusive constrictive pericarditis, due to which it eluded preoperative diagnosis.