Synchronous Multicentric Thymoma

: A 76-year-old man was referred to our hospital because of an abnormal shadow on chest X-ray. His physical exams and laboratory data were not notable. Chest computed tomography (CT) showed 2 nodular lesions with clear margin in anterior mediastinum. The nodule at the left inferior pole of the thymus was 9 cm in diameter, and another one at the right inferior pole was 3.5 cm in diameter. We performed thymo-thymectomy by median sternotomy. Histological study revealed that the left tumor was type B2 thymoma and the other one was type A thymoma. Both were completely encapsulated without invasion, which means stage Ⅰ by Masaoka's classification. The patient has showed no evidence of recurrence for 11 years following the surgery. This is the 1st case in Japan that reported synchronous multicentric thymoma with apparently different histology of type A and B2.