A 54-year-old man was referred to our institution with hemoptysis and hoarseness of 1 year's duration. A computed tomography (CT) scan showed an anterior mediastinal mass (2.5 cm x 1.0 cm), which was diagnosed as thymoma. The tumor was resected under a sternotomy. The tumor had invaded the anterior wall of the ascending aorta. With the patient under cardiopulmonary bypass, the aortic wall invaded by the mass was resected, and arterial reconstruction was performed with patch material. The tumor was revealed to be a tumor of neuronal origin. The patient's postoperative course was uneventful. The patient was discharged on postoperative day 9. One year after the operation, a follow-up chest CT evaluation showed no specific complications or recurrence.