NPM1 and chronic myelomonocytic leukemia: NPM1 mutations are disease-defining genetic lesions serving as gatekeepers for AML,1,7,8 whereas FLT3 mutations are considered late events.9,10 Although NPM1 mutations are most commonly found in AML, they have also been described in other myeloid neoplasms (MNs), including CMML and myelodysplastic syndrome (MDS).