Interestingly, Itzykson et al. observed that, although not yet considered an AML-defining lesion, the presence of NPM1 mutation in CMML tends to be associated to an aggressive clinical course, suggesting that finding NPM1 mutations may favor a diagnosis of de novo AML exhibiting dysplastic features and monocytic differentiation, belonging to M4 or M5 AML subgroups according to former FAB classification, rather than CMML [90]. The gene discussed is NPM1; the disease is chronic myelomonocytic leukemia.