FLT3 and leukemia: Establishing to what degree FLT3 plays a direct role in regulating already lymphoid‐programmed progenitors, is of particular relevance for the high prevalence of two types of FLT3 driver mutations, internal tandem duplication (ITD) and recurrent FLT3 point‐mutations, both associated with a poor clinical outcome in acute leukaemia (Stirewalt & Radich, 2003; Tsapogas et al, 2017), including distinct ETP and B‐cell progenitor leukaemia (Armstrong et al, 2004; Neumann et al, 2013).