The most relevant changes introduced by the WHO and ICC in the classification of chronic myelomonocytic leukemia (CMML) and premalignant monocytosis. Both WHO and ICC systems lowered the cutoff for absolute monocytosis to ≥0.5×109/L absolute monocyte count, thereby incorporating cases formerly referred to as oligomonocytic into the diagnosis of CMML. In addition, both classification systems recognized proof of clonality as a key criterion for defining CMML, leading to the exclusion of cases without evidence of clonal hematopoiesis. Finally, both classification systems introduced myeloid neoplasm precursor states relevant to CMML, under the broad definition of clonal cytopenia of undetermined significance (CCUS) or a specific category of clonal monocytosis of undetermined significance (CMUS). Professional illustration by Somersault18:24.
