BCR and acute lymphoblastic leukemia: In adult patients with ALL, younger age, high white blood cell count, extramedullary disease, mature B cell or T cell immunophenotypes, Philadelphia chromosome positivity (t(9;22) leading to the BCR-ABL fusion gene) or BCR-ABL-like disease, and rearrangements in KMT2A may be associated with increased risk of CNS involvement [11, 12].