FLT3 and acute myeloid leukemia: Specifically, we found PTK2 overexpression to be an independent prognostic factor that distinguishes a patient subgroup with poor outcome among those with IR-AML cytogenetics and non-favorable FLT3/NPM1 combinations, only when they also underexpress PTK2B or LYN. We believe this finding is important because it may identify a subgroup with very poor prognosis (patients with PTK2 overexpression and PTK2B or LYN underexpression) within the highly heterogeneous patients bearing non-favorable FLT3/NPM1 combinations.