Thymomas and thymic carcinomas. Evaluation of the Müller-Hermelink classification.

In the present study the Müller-Hermelink classification was used to analyze 39 thymomas and 4 thymic carcinomas collected over 20 years at the Chair and Department of Pathomorphology CM UJ. Our series consisted of 10 medullary thymomas (25.6%), 13 mixed (33.3%), 7 organoid (17.9%) and 9 cortical thymomas (23.0%). The mean age of the patients was 50.3 and it was the highest in patients with mixed thymomas-58.4 years and the lowest in patients with organoid thymomas-38.9 years, the difference being statistically significant. In the present series women were predominant (24:15). Myasthenia gravis was observed in 10 patients (25.6%), 5 women and 5 men, in 7 of them it was associated with cortical and organoid thymomas. Medullary, mixed and organoid thymomas were usually of lower stage (I and II), having a better prognosis than cortical thymomas and thymic carcinomas. One organoid thymoma recurring after 7 years evolved into cortical thymoma. Two thymic carcinomas were diagnosed as anaplastic, low differentiated, one as sarcomatous and one as well differentiated squamous carcinoma. The mean age of the patients was 39.7 years. The prognosis in all the patients with thymic carcinoma was poor. Based upon personal experience the authors regard the Müller-Hermelink classification as useful, easy to apply, reproducible and providing important prognostic information.