FLT3 and leukemia: Despite the established role of FLT3 in B‐ and T‐lymphopoiesis (Mackarehtschian et al, 1995; McKenna et al, 2000; Sitnicka et al, 2003, 2007; Buza‐Vidas et al, 2007), and the involvement of recurrent FLT3 mutations in acute B‐ and T‐cell progenitor leukaemia (Carow et al, 1996; Gilliland & Griffin, 2002; Armstrong et al, 2004; Neumann et al, 2013), it has remained unclear whether lymphoid‐restricted progenitors are directly dependent on FLT3.