RT-PCR (reverse transcription PCR), performed on patient 7 and two additional iAMP21-ALL samples (patients 11 and 21), confirmed that the normal and mutant FLT3 alleles were transcriptionally expressed in cases harbouring FLT3-ITD at 4–13% VAF (Figure 4e). The gene discussed is FLT3; the disease is acute lymphoblastic leukemia.