Despite the ~two fold increased breast cancer risk in heterozygous ATM mutation carriers (Renwick et al., 2006; , Ahmed and Rahman, 2006) and 1–2% carrier rate in Caucasians, truncating ATM mutations are exceedingly rare (<1/400, in contrast to the predicted 8%) in early-onset breast cancers patients (FitzGerald et al., 1997). Here, ATM is linked to breast cancer.