**3. Chromosomal and molecular abnormalities associated with ALL-B**

60–80% of patients with ALL have abnormalities in chromosome number or structural rearrangements (translocations), whereas the remaining 20–40% have normal karyotype [9, 10]. Besides those with a normal karyotype, t(9;22)(q34,q11); BCR/ABL (BCR-ABL1), t(12;21)(p13;q22);TEL/AML1 (ETV6-RUNX1), t(4;11) (q21;q23); MLL/AF4 (KMT2A/AFF1), t(1;19)(q23;p13); E2A/PBX1 (TCF3-PBX1), are the most common cytogenetic subtypes in ALL [10–12].
