DNA-ploidy analysis correlates with the histogenetic classification of thymic epithelial tumours

The ploidy values of the epithelial component were determined in a series o f thymomas and organotypic thymic carcinomas using image cytometry and the results mere compared with the histological tumour subtypes according to th e histogenetic classification introduced by Marine, Muller Hermelink, and K irchner (MMHK). Forty-six cases of thymic epithelial tumours were included in the study. After reclassification according to the MMHK classification, the distribution among the subtypes was as follows: three medullary, nine m ixed type, five predominantly cortical (organoid), 16 cortical thymomas, an d 13 well-differentiated thymic carcinomas. Single cell preparations were m ade from paraffin-embedded tumour tissue and stained according to Feulgen. Ploidy analysis was performed using an automated image analysis system. In five cases, DNA cytometry could not be performed, for technical reasons. Th e remaining 41 cases consisted of 11 diploid and 30 non-diploid tumours. Th e percentage of aneuploid rumours in the different subtypes increased from medullary (0 per cent) through mixed type (44.4 per cent), predominantly co rtical (75 per cent), cortical (83.3 per cent) to well-differentiated thymi c carcinomas (100 per cent). DNA-ploidy determination using image cytometry correlates with the concept of the MMHK classification of thymomas. Copyri ght (C) 1999 John Wiley & Sons, Ltd.