The World Health Organization (WHO) classification of the myeloid neoplasms

Abstract

A World Health Organization (WHO) classification of hematopoietic and lymphoid neoplasms has recently been published. This classification was developed through the collaborative efforts of the Society for Hematopathology, the European Association of Hematopathologists, and more than 100 clinical hematologists and scientists who are internationally recognized for their expertise in hematopoietic neoplasms. For the lymphoid neoplasms, this classification provides a refinement of the entities described in the Revised European-American Lymphoma (REAL) Classification-a system that is now used worldwide. To date, however, there has been no published explanation or rationale given for the WHO classification of the myeloid neoplasms. The purpose of this communication is to outline briefly the WHO classification of malignant myeloid diseases, to draw attention to major differences between it and antecedent classification schemes, and to provide the rationale for those differences. ( IntroductionRecently, the World Health Organization (WHO), in conjunction with the Society for Hematopathology and the European Association of Hematopathology, published a new classification for hematopoietic and lymphoid neoplasms. 1 The concepts that underlie this classification were derived from numerous published clinical and scientific studies and from the experience of more than 100 pathologists, clinicians, and scientists from around the world who collaborated to develop this consensus classification. 2 A basic principle of the WHO system is that the classification of hematopoietic and lymphoid neoplasms should utilize not only morphologic findings but also all available information, including genetic, immunophenotypic, biologic, and clinical features to define specific disease entities. Essentially, the WHO classification attempts to incorporate those disease characteristics that have proved to have clinical and biologic relevance into a useful, working nomenclature.For the lymphoid neoplasms, the WHO classification provides refinement of the entities defined in the Revised EuropeanAmerican Lymphoma (REAL) Classification-a system that is now widely used by pathologists and clinicians. 3 The WHO classification of myeloid neoplasms includes many of the criteria of the French-American-British (FAB) Cooperative Group classifications of acute myeloid leukemia (AML) 4 and myelodysplastic syndromes (MDS) 5 as well as guidelines of the Polycythemia Vera Study Group (PVSG) for the chronic myeloproliferative diseases (CMPDs), 6,7 but there are some significant differences. The purpose of this communication is to outline briefly the WHO classification of the myeloid neoplasms, to draw attention to major differences between the WHO and previous classifications of these disorders, and to provide the rationale for these differences. In addition, we wish to address and clarify specific issues concerning the classification that have appeared both prior and subsequent to the publication of the WHO monograph. The WHO classification of the myeloid neop...

Phenotypic variations and new mutations in JAK2 V617F–negative polycythemia vera, erythrocytosis, and idiopathic myelofibrosis

“…The World Health Organization (WHO) currently classifies PV, IMF and ET together with chronic myelogenous leukemia, chronic eosinophilic leukemia, chronic neutrophilic leukemia, the hypereosinophilic syndrome and unclassifiable chronic myeloproliferative disease under the rubric of the chronic myeloproliferative disorders (18). However, PV, IMF and ET have more in common phenotypically with each other than with these other disorders and this was confirmed genotypically by the discovery of the JAK2 V617F mutation(6), the expression of which is largely confined to PV, IMF and ET (19).…”

Clinicopathologic analysis of acute myeloid leukemia arising from chronic myelomonocytic leukemia

“…All of the acute myeloid leukemia ex chronic myelomonocytic leukemia cases with NPM1 and/or FLT3 mutation and available cytogenetic results had a normal karyotype. The 5 acute myeloid leukemia ex chronic myelomonocytic leukemia cases with NPM1 mutation had progressed to acute myeloid leukemia from [20] 46,XX,t(11;11)(p15;q23.1) [20] No 44,XY,del(2)(q13),-4,der(5)t(2;5)(q13;q13),-7,12, þ mar [3]/ 46,XY,t(7;21)(p13;q22),del(13)(q12q22) [2]/46,XY [7] 45,XY,t(7;21)(p12;q22),del (13) Transformed chronic myelomonocytic leukemia EL Courville et al chronic myelomonocytic leukemia in 0.5, 3, 3, 6, and 29 months; the acute myeloid leukemia case with unknown NPM1 mutation status but arising from NPM1-mutated chronic myelomonocytic leukemia had progressed to acute myeloid leukemia in 0.5 months.…”

“…2 In 2001, the World Health Organization (WHO) subsequently classified chronic myelomonocytic leukemia within the group of myelodysplastic syndrome/ myeloproliferative disease neoplasms, but no longer distinguished proliferative and dysplastic subtypes. 3 Instead, the WHO recognized two subcategories (chronic myelomonocytic leukemia-1 and chronic myelomonocytic leukemia-2) based on the number of peripheral blood and bone marrow blasts, which appear to be the most important factors in predicting prognosis of chronic myelomonocytic leukemia patients. [4][5][6] Chronic myelomonocytic leukemia progresses to acute myeloid leukemia in up to one third of cases.…”

ATM mediates constitutive NF-κB activation in high-risk myelodysplastic syndrome and acute myeloid leukemia

“…MDS patients were previously untreated except for supportive care. The diagnosis of MDS was based on peripheral blood counts, cytology of peripheral blood and BM according to the WHO classification (Vardiman et al, 2002) and conventional cytogenetic analysis. These data evaluation of the individual IPSS score were assessed for each patient (Greenberg et al, 1997).…”