EVALUATION OF A HISTOGENETIC CLASSIFICATION FOR THYMIC EPITHELIAL TUMORS

We reviewed 87 thymic epithelial tumours from Chinese patients and typ ed them according to the Marine and Muller-Hermelink classification as updated by Kirschner and Muller-Hermelink in 1989. Related categories were grouped for statistical analyses: group 1, medullary thymoma and mixed thymoma; group 2, cortical predominant thymoma; group 3, cortic al thymoma and well-differentiated thymic carcinoma; group 4, other th ymic carcinomas; and group 5, unclassified. Group 3 tumours were more frequently associated with the myasthenia gravis syndrome compared wit h group 1 tumours (P = 0.001). They also presented at a more advanced stage. Groups 1 and 2 showed an excellent prognosis (100% survival at 10 years). The 10-year survival for groups 3 and 4 patients was 40% an d 30% respectively. Pure medullary thymoma made up a higher proportion of our cases (10.3%) than those of a similar Caucasian study (5.3%). The eight thymic carcinomas (group 4) included two thymic lymphoepithe liomas. We conclude that the histogenetic classification evaluated sho ws a clear correlation with prognosis and clinical features, even when tested on separate geographic groups, where pathogenetic factors may be different. A common approach to classification of thymic epithelial tumours would greatly facilitate future studies on these possible dif ferences.