According to the 2022 ICC classification,2 the presence of an NPM1 mutation in CMML should be noted but is not sufficient to define de novo AML.2 In contrast, the 2022 WHO classification proposes that the detection of NPM1 mutation is sufficient to diagnose AML regardless of the blast count in MDS context, but it does not specify in the CMML context.1 A patient with NPM1mut MDS would be diagnosed with AML,1,2 but should a patient with NPM1mut CMML with ≥ 10% blasts also be diagnosed with AML? This evidence concerns the gene NPM1 and myelodysplastic syndrome.