NPM1 and leukemia: Given their frequency in myeloid leukemia (Cancer Genome Atlas Research Network, 2013) and the fact that they are not late mutations (Krönke et al., 2013; Shlush et al., 2014), this observation frames NPM1 mutations as “gatekeepers” of leukemogenesis, i.e., their acquisition appears to be closely associated with the development of frank leukemia.