[Invasive thymoma with thymic cyst; report of a case].

A 27-year-old woman was pointed out an abnormal shadow on chest X-ray in 1999. Because of the enlargement of the chest abnormal shadow, she was admitted to our hospital in 2000. Chest computed tomography (CT) revealed anterior mediastinal solid mass with cystic lesion. A thymoma was suspected. The tumor was removed in June 2000, through a longitudinal incision of the sternum. There was a severe adhesion between the tumor and the right brachiocephalic vein. Histological examination revealed a thymoma with thymic cyst. The thymoma had a capsular invasion (stage II). There were few reports for cases of thymoma with thymic cyst.