ATM and mantle cell lymphoma: The other key alterations that play a role in MCL pathogenesis include deletion of CDKN2A locus that encodes p16, a member of the INK4 family of cyclin-dependent kinase inhibitor, amplification of BMI1 that inhibits CDKN2A, deregulation of TP53 via mutation or deletion, MDM2 overexpression, and ATM deletion (1, 2, 5).