[Cognitive aspects and problems in the diagnosis of malignant tumors and their integration into a general disease...

The view is expressed that the histologic diagnosis of malignant tumors rests on criteria which only partially reflect the true nature of the process. Future development will require a broadened basis for histologic tumor diagnosis. Immunohistochemistry will play an important role. Further as yet undefined methodologic advances are to be expected. Tumor development, like aging, may be regarded as a fundamental biological event and an expression of complex alterations of the genome. It would be a simplification to regard it merely as a manifestation of disturbed growth and differentiation processes. The current oncogen theory represents a useful contribution but is not a complete explantation of tumorgenesis. A definition of malignancy is proposed which incorporates our current understanding of essential aspects and which is distinct from general concepts of disease and from other DNA-related disturbances of development, such as congenital enzyme defects and genetically determined malformations.