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. This evidence concerns the gene FLT3 and acute myeloid leukemia.