NPM1 and acute myeloid leukemia: On the other hand, FLT3 internal tandem duplications (ITD) were shown to be less common in elderly compared to younger AML patients (23% and 37%).16 Both NPM1 mutation and FLT3 ITD have been reported to be under-represented in elderly normal karyotype AML compared to younger patients (52.1% and 66.4% for NPM1 mutation; 26.6% and 37.2% for FLT3-ITD, respectively).9 The frequency of both NPM1 mutations and FLT3-ITD are significantly lower in t-AML compared to de novo AML, indicating that secondary leukemogenesis might follow mechanisms different from those seen in de novo AML.