Clinicopathological study of thymomas--correlation of histologic subtype to myasthenia gravis and prognosis.

Thymoma is the most common primary tumor of anterior superior mediastinum. Sixty cases of thymomas over a 12 year period were analysed and the histologic subtype, according to Marino and Muller-Hermilink, classification was correlated with presence or absence of myasthenia gravis (MG) and capsular invasion. Thirty four patients had myasthenia gravis associated with thymoma and there was one case of pure red cell aplasia. There were 3 (1) predominantly cortical, 28 (20) cortical, 12 (9) mixed, 16 (4) medullary thymomas and 1 (0) thymic carcinoma (Figures in parenthesis indicate number of cases associated with MG). Capsular invasion was seen in 25 cases. Association with myasthenia gravis and capsular invasion were seen predominantly in cortical and mixed thymomas which were also associated with aggressive behaviour.