Neoplastic Diseases of the Hematopoietic and Lymphoid Tissues: New World Health Organization Classification

Yang, Woo Ick

Abstract

Encouraged by the success of the Revised European American Classification of Lymphoid Neoplasms (REAL) which was published in 1994 by th International Lymphoma Study Group (ILSG), the European Association of Pathologists and the Society for Hematopathology have started a collaborative classification project in 1995 under the auspices of World Health Organization (WHO). The two collaborators employed the same consensus building process used by ILSG for the REAL to the classification of myeloid, histocytic/dendritic, and mast cell neoplasms and listed real biologic entities defined by morphologic, immunophenotypic, cytogenetic, and and clinical findings. In contrast to the REAL, Clinical Advisory Committee composed of expert hematologists and oncologists evaluated the clinical relevance of the classification scheme proposed by the pathologists before the publication of new WHO classification of hematologic malignancies. While the classification of lymphoid neoplasms contained minor changes compared with the REAL, there were major changes in the classification system of myeloid neoplasms compared with the previously used French-American-British (FAB) classification. The new WHO classification of hematologic malignancies, published last year, is a product of the first true worldwide consensus among leading pathologists and clinicians alike, and it overcomes the drawbacksof old fashioned classification schemes; therefore, we can expect progress in the understanding and treatment of hematologic malignancies.