NOTCH1 and B-cell chronic lymphocytic leukemia: Interestingly, even independent of explicit NOTCH1 mutations, roughly 50% of CLL cases in one series had a NOTCHhigh gene expression signature and another series found increased activated NOTCH1 by immunohistochemical staining in over 80% of cases, suggesting that Notch ligands drive signalling in CLL even with a non-mutated Notch receptor [26,27].