ATM and neoplasm: When we restricted the analysis to the 16 tumours in which biallelic inactivation of ATM was demonstrated (i.e., breast tumours from A-T participants and breast tumours from HetAT participants showing LOH at the ATM locus), we found that copy number losses at 8p, 11q, 13q and 22q corresponded to longer chromosome segments than the ones described in the 23 ATM-associated tumours.