Lymphoma classification: the quiet after the storm.

The classification of malignant lymphomas remained controversial for over 30 years. The first scheme was proposed by Rappaport in the '60th and was based on incorrect histogenetic concepts. To overcome these limitations, several groups formulated new proposals in '70th. Among these two merited attention: the Lukes and Collins and the Kiel Classifications. They were based on the assumption that each lymphoma category might be related to a precise differentiation step of the lymphoid system, thus excluding any correlation with histiocytes, present on the Rappaport scheme. The Kiel Classification became very popular in Europe, while the one of Luke and Collins did not meet success in the United States (U.S.). In 1978, the National Cancer Institute proposed an international trial to compare the classifications used in Europe and U.S. The result was the genesis of the Working formulation, the tool for lymphoma classification in the U.S. up to the early '90th, but which was conversely rejected in Europe. In order to get over this lack of transatlantic communication, in 1994 the Revised European-American Lymphoma (REAL) Classification was proposed by the International Lymphoma Study Group. Its goal was to list "real" entities, each defined by the presence of homogeneous morphologic, phenotypic, cytogenetic, molecular, and clinical criteria, along with the possible recognition of its normal counterpart. The REAL Classification became the model for the WHO Classification of all haematopoietic tumours published in 2001. The present review aims to analyse future perspectives after the fourth edition of the WHO Classification released in 2008.