In a major revision to the classification of myeloid neoplasms and acute leukemias, an independent classification outside of the World Health Organization (WHO) has been developed and published by a leading group of experts.
“This new classification represents a major revision of the prior classifications and includes many authors of the prior WHO editions but is no longer affiliated with the WHO,” the authors, led by Daniel A. Arber, MD, of the University of Chicago Medicine, wrote.
The new report, called the International Consensus Classification (ICC) of myeloid neoplasms and acute leukemias, integrates morphologic, clinical, and genomic data of these disorders. The revised classification was developed by a team of hematologist oncologists, pathologists, and other experts with knowledge of these disorders.
The need for revisions and updates to the standards has been driven by the rapid acquisition of new knowledge since the 2016 WHO classification, according to Dr. Arber and colleagues.
“The recent advances in our understanding of the biology of hematologic malignancies, the experience with the use of the 2016 WHO classification in clinical practice, and the results of clinical trials have indicated the need for further revising and updating the classification,” they wrote.
Dr. Arber and colleagues wrote that main the motivation for the report was to refine the disease entities. For example, in the case of systemic mastocytosis (SM), the previous subtype “SM with an associated hematologic neoplasm” (SM-AHN) was changed to “SM with an associated myeloid neoplasm” (SM-AMN), which allows a better framing of this disease entity, since research has demonstrated that the “hybrid” uniqueness of SM-AHN was limited to the presence of an associated myeloid neoplasm, with which it often also shares a KIT mutation or other clonal genetic abnormalities.
Also, in the case of myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN), the “unclassifiable” diagnosis (MDS/MPN U), which was previously largely a diagnosis of exclusion, has been renamed “not otherwise specified” (MDS/MPN NOS), since the disease entity is now better refined with the adoption of newly specified diagnostic requirements.
“The main objective of the consensus process was the definition of real disease entities, including the introduction of new entities and refined criteria for existing diagnostic categories, based on accumulated data,” the authors wrote.
The authors noted that the report was necessary given that major advances have happened since the last WHO classification was published in 2008 (in 2016 a revised edition of the 2008 classification was published as well).
“The revised fourth edition WHO classification, published in 2016, was tasked to not be a major overhaul of disease categories but simply as an update based on new knowledge,” the authors wrote. “Major advances in the understanding of myeloid neoplasms and acute leukemia have occurred since the original fourth edition publication in 2008, and a more significant change to disease classification is now warranted.”
Arber DA, Orazi A, Hasserjian RP, et al. International consensus classification of myeloid neoplasms and acute leukemias: integrating morphologic, clinical, and genomic data. Blood. 2022;140(11):1200-1228. doi:10.1182/blood.2022015850