FLT3 mutation types ranged from substitutions to indels and varied according to the ALL subgroup in which they occurred; while substitutions and indels were common in high hyperdiploid and B-other ALL, FLT3-ITD was significantly more prevalent in iAMP21-ALL (χ2 test, ITD versus non-ITD in iAMP21 and non-iAMP21-ALL, P=0.0001). Here, FLT3 is linked to acute lymphoblastic leukemia.