FLT3 is a cytokine receptor which belongs to the receptor tyrosine kinase class III. It is expressed on the surface of many hematopoietic progenitor cells. Signaling of FLT3 is important for the normal development of haematopoietic stem cells and progenitor cells. The FLT3 gene is one of the most frequently mutated genes in acute myeloid leukemia (AML). High levels of wild-type FLT3 have been reported for blast cells of some AML patients without FLT3 mutations.