[The new WHO classification of liver tumors--what is really new?]

The new WHO (2000) Classification comprises all gastrointestinal tumours including tumours of the liver and intrahepatic bile ducts. The differences between the old edition from 1994 and the new classification will be outlined. A comparison was made with regard to new entities, definitions and tumor subtypes. The eight tumour subgroups of the 1994 classification have been reduced to seven in the 2000 WHO edition, omitting the "unclassified tumors" and changing the group's terms. The 2000 classification shows some minor changes in the ICD-O numbers and in terminology. An important change and hopefully beneficial progress has been achieved by introducing more detailed definitions of epithelial abnormalities, namely liver cell dysplasia and its different subtypes (large cell type dysplasia, small cell type dysplasia, dysplastic nodules low-grade and high-grade). The miscellaneous lesions (former called tumour-like lesions) have been reduced in number. In contrast to the 1994 classification which only contained definitions and short descriptions of macroscopic and microscopic findings as well as only sparse clinical information, the 2000 classification offers much more text with new information on epidemiology, aetiology, clinical features, spread, macroscopy, microscopy, genetic susceptibility, and genetics. Some minor differences between the old and new WHO classification can be recognized. Major changes comprise the extended terminology in precancerous epithelial changes, e.g., liver cell dysplasia and reduction of the amount of text.