RESUMEN
A 46-year-old man presented with mass on chest x-ray along with a 6-month history of weight loss, dyspnea and cough. He was hypotensive and an echocardiogram showed large extra-cardiac mass compressing the right ventricular outflow tract resulting in features of cardiac tamponade. Chest computed tomography revealed a mediastinal mass invading the pericardium adjacent to right ventricular outflow tract. Biopsy of the mass confirmed primary monophasic synovial sarcoma. Chemotherapy and radiotherapy along with anti-inflammatories were given as surgery was too high risk due to the location of the tumour and pericardial involvement. Patient responded briefly to the treatment with improvement in hemodynamic parameters but over next weeks he became less responsive to treatment with increasing size. He died 2 months after treatment commenced.