World Health Organization classification of neoplastic diseases of the hematopoietic and lymphoid tissues: Report of the Clinical Advisory Committee Meeting - Airlie House, Virginia, November 1997

Purpose: The European Association of Hematopathologists and the Society for Hematopathology have developed a new World Health Organization (WHO) class ification of hematologic malignancies, including lymphoid, myeloid, histioc ytic, and mast cell neoplasms, Design: Ten committees of pathologists developed lists and definitions of d isease entities. A clinical advisory committee (CAC) of international hemat ologists and oncologists was formed to ensure that the classification would be useful to clinicians, The CAC met in November 1997 to discuss clinical issues related to the classification. Results: The WHO uses the Revised European-American Lymphoma (REAL) classif ication, published in 1994 by the International Lymphoma Study Group, to ca tegorize lymphoid neoplasms. The REAL classification is based on the princi ple that a classification is a list of "real" disease entities, which are d efined by a combination of morphology, immunophenotype, genetic features, a nd clinical features. The relative importance of each of these features var ies among diseases, and there is no one gold standard, The WHO classificati on applies the principles of the REAL classification to myeloid and histioc ytic neoplasms. The classification of myeloid neoplasms recognizes distinct entities defined by a combination of morphology and cytogenetic abnormalit ies. At the CAC meeting, which was organized around a series of clinical qu estions, participants reached a consensus on most of the questions posed. T hey concluded that clinical groupings of lymphoid neoplasms were neither ne cessary nor desirable. Patient treatment is determined by the specific type of lymphoma, with the addition of grade within the tumor type, if applicab le, and clinical prognostic factors, such as the International Prognostic I ndex. Conclusion: The WHO classification has produced a new and exciting degree o f cooperation and communication between oncologists and pathologists from a round the world, which should facilitate progress in the understanding and treatment of hematologic malignancies, J Clin Oncol 17:3835-3849, (C) 1999 by American Society of Clinical Oncology.