As a secondary genetic event in the development of leukemia, the CDKN2A/B deletions were found in approximately 20%–25% of B-cell precursor acute lymphoblastic leukemia (BCP-ALL) and 38.5%–50% of T-ALL patients (2, 5, 7, 8). The gene discussed is CDKN2A; the disease is precursor B-cell acute lymphoblastic leukemia.