CDKN2A and acute lymphoblastic leukemia: Deletions within chromosomes 7 and 9, including IKZF1 and CDKN2a/b genes, are also frequently accompanied by IGH and TCR gene deletion in Ph-positive BP-ALL [66], indicating that deletion of the IGH and/or TCR gene region is obligatory for the development of a malignant clone with a lymphoid phenotype.