AML with mutations in the NPM1 gene morphologically displays the features of myeloblastic leukemia with or without differentiation (predominant blast cells, cytoplasmic granules, irregular nuclei and heterogeneous subtypes) and those of acute leukemia with monocytic/monoblastic differentiation (undifferentiated cells, differentiation based on monocytic-lineage blast cells, prominent blast morphology). This evidence concerns the gene NPM1 and acute myeloid leukemia.