We identified putative subclonal mutations representing 3–20% of reads in four leukaemic samples: (i) a FLT3 internal tandem duplication in sample P3, which was flagged as a series of indels and substitutions and confirmed by PCR (we went on to test all seven AML samples for FLT3-internal tandem duplication and only sample P3 was positive—data not shown), (ii) NRAS-G12S and PTPN11-Q506P mutations in sample P5. The gene discussed is FLT3; the disease is acute myeloid leukemia.