ABL1 and acute lymphoblastic leukemia: At present, however, from the clinical point of view, only one subtype, i.e., Philadelphia chromosome-positive (Ph+) ALL, characterized by the presence of a t(9;22)(q34.1;q11.2) and corresponding BCR-ABL1 gene rearrangement requires particular treatment, while for the remaining ones (Philadelphia-negative, Ph- ALL) the first-line therapy is relatively consistent.