9p21.3 deletions, which lead to the loss of CDKN2A/INK4A/p16, CDKN2B/INK4B/p15, and MTAP/ARF/p14 tumor suppressor genes expression, are the most predominant aberrations seen in precursor B-cell ALL (~20% of the cases) and T-ALL (>60% of the case) [39–42]. The gene discussed is MTAP; the disease is acute lymphoblastic leukemia.