Recurrence of thymoma: clinicopathological features, therapy, and prognosis.

Factors influencing the recurrence or persistence of thymoma after therapy were investigated in 127 patients with thymoma, including 75 with thymoma and myasthenia gravis. The rate of recurrence or persistence was 19% (24 of 127 patients) overall, 11% (8 of 75 patients) in myasthenic thymoma, and 31% (16 of 52 patients) in nonmyasthenic thymoma. The more advanced the clinical stage, the higher the rate of recurrence or persistence. The recurrence/persistence rate for patients with the same clinical stage was higher in those with nonmyasthenic thymoma (8% in Stage I, 11% in Stage II, 36% in Stage III, and 75% in Stage IV) than in those with myasthenic thymoma (0 in Stage I, 13% in Stage II, 18% in Stage III, and 20% in Stage IV). The prognosis for patients having subtotal resection of tumor was good in myasthenic thymoma (recurrence/persistence rate, 17%) in contrast with nonmyasthenic thymoma (recurrence/persistence rate, 78%). These results suggest that nonmyasthenic thymoma is more malignant than myasthenic thymoma. Postoperative radiotherapy was effective in preventing the recurrence or persistence of thymoma after therapy.