BCR and acute lymphoblastic leukemia: Moreover, activating mutations in NOTCH1 occur in up to 75 % of T-ALL (Liu et al., 2017), the BCR::ABL1 fusion is the oncogenic driver of Philadelphia chromosome-positive (Ph+) ALL (Bernt & Hunger, 2014), rearrangements of KMT2A involving multiple fusion partners are drivers of most cases of infant ALL as well as many cases of childhood AML (Meyer et al., 2023), and FLT3 activating mutations are observed in leukemias (Grobner et al., 2018; Ma et al., 2018).