FLT3 and acute lymphoblastic leukemia: In two studies, SH2B3 abnormalities co-occurred recurrently with potentially synergistic IL7R and/or FLT3 activating mutations [28, 31], prompting us to investigate IL7R/JAK/STAT, FLT3/STAT and FLT3/RAS/RAF/ERK signalling pathways in iAMP21-ALL.