FLT3 and acute myeloid leukemia: The receptor tyrosine kinase FLT3 is expressed at high levels in almost all AML, and >30% of AML bears an oncogenic FLT3 mutation.2 The most common FLT3 mutation is an internal tandem duplication (ITD) of the sequence that encodes the juxtamembrane domain, which portends a poor prognosis.