Primary cardiac angiosarcoma of the right atrium undiagnosed by transvenous endocardial tumor biopsy.

A 50-year-old man was admitted with acute pericarditis. Echocardiography demonstrated a large mass on the right atrial free wall along with a pericardial effusion. We performed transvenous biopsy of this mass under transesophageal echocardiographic guidance. Though the biotome obtained the mass, the pathological findings were of organized thrombus. Two weeks later, a new precordial mass appeared around the left third rib and was suspected to be a metastasis. Incisional biopsy of this mass gave the diagnosis of angiosarcoma.