NPM1 and acute myeloid leukemia: Based on previous evidences establishing the FAK protein as a poor prognostic factor in AML patients [19,20,22], and the fact that PTK2 (gene encoding for FAK protein) was not identified as prognostic factor for clinical outcome in IR-AML in our study, we decided to assess PTK2 expression in the patient subset with worst prognosis in our series, which were those showing underexpression of PTK2B or LYN and non-favorable FLT3/NPM1 combinations (N = 164).