Histopathological classification of Hodgkin's lymphomas. Results from the reference pathology of the German Hodgkin...

Diagnostic biopsies of 1,140 previously untreated patients with Hodgkin's lymphoma from the German Hodgkin Therapy Trial were evaluated by a panel of 4 histopathologists. Each case was classified by consensus of the four according to an extended Rye-System including the diversifying of NS.HD and the unclassifiable cases. The interobserver agreement rate was 92.1% among the panel members regarding the final classification. Primary Hodgkin diagnosis was approved in 91.7% (1045/1140 cases). The distribution of the 1,140 cases within this system was (in %) as follows: 2.7 LP.HD, 57.9 NS.HD, 17.3 MC.HD, 0.7 LD.HD, 13 HD of unclassifiable subtypes, 6.3 of not certain HD, 1.9 Non-Hodgkin Lymphoma, 1 case of non malignancy. Grading of NS.HD into 2 subgroups according to the British classification differed conspicuously by 84.5% versus 15.5% and 71.6% versus 28.4% in British results. This divergency is explained by interobserver disagreement ranking from 43% to 85%.