[Clinical evaluation of classifications of malignant lymphoma from the viewpoint of history]

The classification of malignant lymphoma has been modified several times in this century and has often been a source of confusion for clinical oncologists. This review deals with the historical aspects of lymphoma classifications from the viewpoint of clinical relevance. Until recently, in the United States and Japan, a Working Formulation (WF) has been used as the main classification system for malignant lymphoma. WF was predominantly based on hematoxilin/eosins morphology, grouping the lymphoma subtypes according to their overall survival. Since WF was proposed in 1982, the development of immunophenotypic and molecular genetic analyses has enabled us to identify several previously unrecognized disease entities with distinct histopathological and clinical features. In 1994, based on such development, the International Lymphoma Study Group proposed a new classification, the Revised European-American Classification (REAL Classification). The clinical relevance of the REAL Classification is discussed based on recent clinicopathologic studies.