New entities, issues, and controversies in the classification of malignant lymphoma.

The classification of malignant lymphoma has, for decades, provided a fertile area for controversy, discussion, and change. Such debate is necessary in order to appropriately assimilate new knowledge regarding this group of neoplasms. In this review, we provide a brief account of the evolution of classification schemes for lymphoma, and emphasize the recently proposed Revised European-American Lymphoma (REAL) classification as a synthesis of current knowledge of clinical, morphologic, immunologic, and molecular data. Specific entities that are recently described or for which there are current controversies are discussed. The necessity of communication between clinicians and pathologists in the workup of a patient with malignant lymphoma is emphasized.