FLT3-ITD (Fms-like tyrosine kinase 3-internal tandem duplication) is a genetic mutation commonly found in acute myeloid leukemia (AML), a type of blood cancer. FLT3 is a receptor tyrosine kinase involved in the regulation of cell growth and division. When the FLT3 gene undergo internal tandem duplication mutations, it results in the insertion of additional nucleotides within the gene, most often in the juxtamembrane domain (JMD). These mutations lead to the continuous activation of the FLT3 protein, promoting uncontrolled cell proliferation and contributing to the development of AML. This is one of the most frequent mutations found in acute myeloid leukemia (AML) patients, with a frequency of 20–30%.

FLT3-ITD mutation is significant in AML because it is associated with poor prognosis and a higher risk of relapse. Patients with AML who harbor FLT3-ITD mutations often have a more aggressive disease course compared to those without this mutation. Therefore, FLT3-ITD status is an important factor considered in the risk stratification and treatment planning for AML patients.