RUNX1 and leukemia: However, the incidence of the ETV6-RUNX1 fusion is about 100-fold higher than the incidence of ETV6-RUNX1+ B-ALL in children (Mori et al., 2002; Schafer et al., 2018), and a specific environmental context seems to be necessary to turn preleukemic cells into overt leukemia (Greaves, 2018; Cobaleda et al., 2021a,b).