ATM and cancer: Importantly, cancer susceptibility occurs at especially high incidence (10–15%) of lymphoproliferative disorders in childhood or early adulthood.37 In addition to CLL, the region on chromosome 11 containing the ATM gene is frequently deleted in Mantle cell lymphoma and T-cell prolymphocytic leukemia.38 Deletion of 11q has been recognized as a poor prognostic factor for CLL in progression-free survival and overall patient survival.2 Several studies have been conducted to test the clinical significance of ATM mutations in different cohorts of CLL patients.