A Right Atrial Appendage Thrombus Mimicking a Tumor.

A right atrial (RA) mass was incidentally found by transthoracic echocardiography in a 79-year-old man with atrial fibrillation rhythms but without a history of anticoagulation. Transesophageal echocardiography revealed a pedunculated immobile mass in the RA appendage. In addition, some calcification was detected in computed tomography. The mass was excised, and pathological examinations revealed organized thrombosis. Accordingly, in the presence of predisposing factors, thrombi, which may mimic some imaging features of tumors, should be considered in the differential diagnosis of RA masses.