[A case of a small thymoma associated with myasthenia gravis in which the tumor was reduced by corticosteroid therapy].

The case in this study was a 34-year-old male with a small thymoma associated with myasthenia gravis. The patient had been treated with corticosteroids for 10 months against myasthenia gravis. During the course of the treatment a chest CT revealed that the tumor had reduced. Thereafter the extended thymectomy was performed. A close examination of the excised thymus revealed the presence of a flat cystic tumor measuring 1.5 x 0.8 x 0.5 cm at the site corresponding to the CT image. This tumor was histologically ascertained to be a thymoma. The thymoma is sensitive to corticosteroids, which can effectively reduce it. As conclusion, it is necessary to check thoroughly on the presence of thymoma prior to the initiation of corticosteroid therapy to treat myasthenia gravis.