Abstract

Sixty-one patients with thymic tumors were treated at our institution from 1980 to 1995 and were analyzed to compare the prognostic relevance of the Masaoka and Müller-Hermelink classification, respectively. Complete follow-up was achieved in 97% of the patients. The classification according to Masaoka revealed stage I in 46% of the patients, stage II in 25%, stage III in 22%, and stage IV in 7%, with a 10-year survival rate of 83% for stage I, 80% for stage II, 41% for stage III and 0% for stage IV, and a disease free survival of 89% for stage I, 63% for stage II, 35,% for stage III and 0% for stage IV, respectively. The histological reclassification according to Müller-Hermelink revealed medullary thymoma in 10% of the patients, mixed thymoma in 20%, organoid thymoma in 24%, cortical thymoma in 19%, well-differentiated thymic carcinoma in 22% and endocrine carcinoma in 5%. The 10-year survival rate was 100% for medullary thymoma, 88% for organoid thymoma, 70% for mixed thymoma, 63% for cortical thymoma, 21% for well-differentiated and 0% for endocrine carcinoma, and the disease free survival was 100%, 84% 76%, 42%, 24% and 0%, respectively. Medullary, mixed and organoid thymoma were correlated with Masaoka stage I and II; cortical, well-differentiated and endocrine carcinoma were correlated with Masaoka stage III and IV (p < 0.001). A multivariate analysis revealed age, gender, myasthenia gravis and postoperative adjuvant radio- and chemotherapy not as significant independent predictive factors. Our findings suggest that overall survival was related to the Müller-Hermelink classification (p < 0.01) and disease free survival to the Masaoka classification (p < 0.001).