FMS-like tyrosine kinase 3 (FLT3), a type III receptor tyrosine kinase (RTK), is one of the most frequently mutated genes and occurs in approximately one third of AML, with the majority of mutations exhibiting the internal tandem duplication (ITD) in its justamembrance domain [1, 2]. The gene discussed is FLT3; the disease is acute myeloid leukemia.