Carriers of a mutated BRCA1 or BRCA2 gene are at an increased risk of breast (BC) and ovarian cancer (OC); however, penetrance estimates differ in various study populations (Easton et al, 1995; Struewing et al, 1997; Ford et al, 1998; Thorlacius et al, 1998). This evidence concerns the gene BRCA2 and breast cancer.