Editorials and Perspectives

Tumor classification systems provide a means ofcommunication between pathology, clinicalmedicine and basic research to support clinical decision-making, comparison of therapeutic protocols and development of new biological insights. Since the introduction of the Kiel classification in the 1970s, the lymphoma world has been very fortunate as compared to many other tumor systems. The paradigm of a biological foundation based on a normal counterpart hypothesis immediately propelled this classification beyond a mere morphological description. Since then, this principle has been further developed into classifications of lymphoma entities based on integrated morphological, immunohisto-chemical, genetic and clinical criteria. Some classes, such as classical Hodgkin’s lymphoma, marginal B-cell lym-phoma, MALT-type and mantle cell lymphoma, are very well delineated. Others are more complex and pose