Interestingly, genotype-phenotype analyses of BRCA2 breast cancer pedigrees mirror the observations in biallelic BRCA2 mutation cases, with different cancer risks associated with monoallelic truncating mutations in exon 11 when compared with mutations located in 3′ or 5′ of this exon (Thompson et al., 2001; Lubinski et al., 2004). This evidence concerns the gene BRCA2 and breast cancer.