Analysis of FLT3_ITD integration sites from 753 unselected FLT3_ITD-positive AML cases. The localization of ITD integrations together with their respective frequencies and their position relative to functional domains of the receptor are shown for 753 ITD-positive AML patients analyzed. A significant number of ITDs (28.7%) are localized in the first tyrosine kinase domain (TK1) of FLT3. A detailed analysis showed ITD integrations in the β1-sheet of TK1, amino acids 610 to 615, in 24.6%, in the nucleotide binding loop (NBL), amino acids 616 to 623, in 2%, in the β2 sheet, amino acids 624 to 630, in 1.3% and 3′ of the β2 sheet in 0.8% of all cases. The localization of primers used to amplify, sequence, and isolate the ITD627E allele (ITD-f and ITD-r) is depicted. AA indicates amino acid; TM, transmembrane domain; JM, juxtamembrane domain; TK1, tyrosine kinase domain 1; KI, kinase insert; TK2, tyrosine kinase domain 2; and NBL, nucleotide binding loop.