The significance of the classical monocyte subpopulation in chronic myelomonocytic leukemia: a single-center experience

Introduction Chronic myelomonocytic leukemia (CMML) is a myelodysplastic/ myeloproliferative neoplasm. In 2022, updated diagnostic classifications for CMML were introduced by the International Consensus Classification (ICC) and World Health Organization (WHO). Monocytes are subdivided into three populations: classical (MO1), intermediate (MO2), and non-classical (MO3). One of the newly established diagnostic criteria for CMML is an increase in the MO1 fraction to ≥ 94%, as determined by multiparametric flow cytometry (MFC). This parameter has been shown to be a highly sensitive and specific marker that can rapidly and accurately differentiate CMML from other conditions. Material and Methods At the Department of Hematology, Cellular Therapies, and Internal Medicine, University Clinical Hospital in Wrocław, we evaluated the distribution of monocytes and their subpopulations using MFC in 27 patients with newly diagnosed CMML, classified according to the updated WHO criteria. Results The criterion of an MO1 fraction ≥ 94% was fulfilled in 22 patients (81.5%). Conclusions Our findings are consistent with previously published data and support the utility of this method as a reliable tool for both initial screening and longitudinal monitoring of CMML.