Assuming 1) the prevalence of BRCA1 in the breast cancer population is 2 % [5]; 2) 15 % of breast cancers have a basal phenotype [1, 4]; and 3) 69 % of all BRCA1 cancers have a basal phenotype [30], the positive predictive value (PPV) is estimated to be 38 % and the negative predictive value is estimated to be 94 %. This evidence concerns the gene BRCA1 and cancer.