JAK2 and acute lymphoblastic leukemia: Underscoring the importance of JAK2 in the pathogenesis of ALL, Roberts et al. (2014a) reported 5-years event-free survival (EFS) rates of 38.8% for CRLF2r/JAK-mutant ALL patients and 26.1% for ALL patients harboring a rearrangement of either JAK2 or EPOR (Figure 1) (Roberts et al., 2014a), subsequently reported as 23.5% in a later study (Roberts K. G. et al., 2017).