[Right Atrial Thrombus which was Difficult to Differentiate from Tumor;Report of a Case].

We report a case of a 79-year-old woman with a right atrial mass. She had a history of hypertension, idiopathic thrombocytopenic purpura, and chronic atrial fibrillation. Computed tomography and transthoracic echocardiography showed a 31×31 mm mass in the right atrium. Though it was considered to be a thrombus at first, it did not become smaller despite anticoagulation, and tumor was suspected. To prevent onset of pulmonary embolism, she underwent surgery and the mass was removed. Pathological examination confirmed that it was a thrombus. Her postoperative course was uneventful.