Model for development of lymphoid malignancies on the background of inherited or acquired

ATM inactivation. (A) A-T patients with inherited inactivation of both ATM alleles develop both B (B-cell lymphoma) and T-cell tumors, but T-cell tumors are largely predominant. Atm^−/− mice develop only T-cell tumors. (B) Individuals with both germline ATM alleles wild type, can acquire complete ATM inactivation during lymphoid development and develop either B-cell malignancies of pregerminal center origin (B-CLL and MCL) or T-cell tumors (T-PLL). * Patients with sporadic B-CLL can be ATM mutation carriers. In contrast to A-T patients with inherited inactivation of both ATMalleles, B-cell tumors are more common than T-cell malignancies in non–A-T individuals.