FLT3 and acute myeloid leukemia: Interestingly, 4/6 NPM1-mutated AML patients with FLT3 wild-type at diagnosis who relapsed with FLT3-ITD (according to conventional PCR), harbored very small FLT3-ITD subclones already at diagnosis, when analyzed by a highly sensitive patient-specific RT-qPCR for FLT3-ITD [34].