CD34 and acute myeloid leukemia: Moreover, the rare cases of NPM1-mutated MNs, mainly belonging to high-risk MDS and CMML, usually show normal karyotype, negativity for CD34 expression on blasts and aggressive clinical behavior with relatively rapid progression to overt AML, raising controversies on their classification as distinct clinico-pathologic entities [5,69,71,75,79,87,88].