Though less frequent compared with de novo AML, NPM1 mutations have also been observed in secondary AML (defined as progressing from either MDS or myelodysplastic/myeloproliferative neoplasm (MDS/MPN)) with a variable incidence ranging from 4.5% to 27% of cases [108,109,110,111,112,113]. The gene discussed is NPM1; the disease is myelodysplastic syndrome.