The results of these studies are inconclusive, with some studies reporting an increased breast cancer risk (Swift et al, 1987; Pippard et al, 1988; Athma et al, 1996; Stancovic et al, 1998; Inskip et al, 1999; Janin et al, 1999) and others failing to demonstrate such an effect in heterozygote ATM mutation carriers (Vorechovsky et al, 1996; FitzGerald et al, 1997; Bay et al, 1998; Chen et al, 1998). This evidence concerns the gene ATM and breast cancer.