Myeloproliferative neoplasms: changes since the WHO 2016 classification

Abstract

A group of international experts, including haematopathologists, oncologists, and geneticists met on September 2021 in Chicago, IL, USA to update the 2016/17 World Health Organization classification system for haematopoietic tumours. After careful deliberation, the group introduced the new International Consensus Classification (ICC) for Myeloid Neoplasms and Acute Leukaemias. The classification was published in June 2022 (Arber DA, Orazi A, Hasserjian RP, et al. Blood 2022; 140: 1200–1228). This presentation focuses on the ICC-2022 category of chronic myeloid leukaemia (CML), BCR::ABL1 positive and the BCR::ABL1 negative myeloproliferative neoplasms (MPNs): essential thrombocythemia, polycythemia vera, primary myelofibrosis, and MPN, unclassifiable. In CML, ICC recognises three disease phases: chronic (CP), accelerated (AP), and blast (BP) phase. Their definition has been streamlined. For the MPN group, ICC chose to preserve the primary role of bone marrow morphology in disease classification and diagnostics, while also acknowledging the complementary role of genetic markers for establishing clonality, facilitating MPN subtype designation, and disease prognostication. Chronic neutrophilic leukaemia (CNL) can now be diagnosed with a WBC of > 13x 109/L. The diagnosis of chronic eosinophilic leukaemia, NOS, now requires a bone marrow showing dysplastic changes. Reference 1. Thiele J, Kvasnicka HM, Orazi A, et al. The international consensus classification of myeloid neoplasms and acute leukemias: myeloproliferative neoplasms. Am J Hematol 2022; doi: 10.1002/ajh.26751. Epub ahead of print. PMID: 36200127.