Invasive thymoma with myasthenia gravis.

In 261 surgically treated patients with myasthenia gravis (MG), 26 had an invasive thymoma and 49 had a noninvasive thymoma. Invasive thymoma was seen in 41% of thymomatous MG patients older than 40 years of age, and 28% in patients younger than 40 years of age. Of 19 patients who underwent total or subtotal thymothymomectomy accompanied by irradiation (4000 rad), 17 were still alive on an average 6.5 years after surgery. The deterioration of MG by the irradiation was observed in 7 of 20 irradiated cases. Thus, postoperative irradiation is effective but should be done with attention to the deterioration of MG. The prognosis of MG in patients with an invasive thymoma was poorer than that in patients with a noninvasive thymoma.