Pathological Findings of Tumors at Thymus and Myasthenia Gravis

ABSTRACT

We retrospectively studied 53 cases of thymic tumors diagnosed after thymectomy to clearfied the pathologic difference of thymic tumor associated with myasthenia gravis and without myasthenia gravis. Among them, there are 23 cases with myasthenia gravis; 19 among 36 thymomas(52.8%), 3 of 4 thymolipoma (75%) and 1 squamous cell carcinoma. Lymphoma and teratoma are not associated with myasthenia gravis. There is no significant difference in the prevalence of myasthenia gravis between types of the old traditional classification of thymoma. But according to the new Muller-Hermelink classification, about two-thirds of myasthenia gravis have the thymoma with cortical cell origin. The prevalence of myasthenia gavis were relatively low in the patients with thymoma of medullary or mixed type. The frequent association of myasthenia gravis was suggesting that the thymolipoma might be a variant of thymoma, cortical type.