NOTCH1 and acute lymphoblastic leukemia: Activating NOTCH1 mutations are prevalent in hematological malignancies and sequenced in 40% to 70% of T cell acute lymphoblastic leukemia (T-ALL) [16], in 10–15% of chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) [17, 18] and a subset of diffuse large B cell lymphoma (DLBCL) [19].