FLT3 and acute myeloid leukemia: It is known that different ARs of FLT3/ITD demonstrated uneven prognostic significance, and a crucial cut-off value of 0.5 for FLT3/ITD AR has been well established in European LeukemiaNet (ELN 2017)22, which has been reclassified as a favorable risk, but is only restricted to adult AML, whereas the threshold for pediatric AML remains controversial.