Evidence consistently showed that family history of breast cancer in the first-degree relatives (FDR) was associated with 110% (95% confidence interval [95% CI]: 100–120%) excess risk of breast cancer compared with those without a family history[4]; this association, however, might not be entirely attributable to the genetic variations (e.g., BRCA1/2 mutations) and the contributions from shared environmental factors, such as a prolonged exposure to endogenous and exogenous female sex hormones in a familial microenvironment, could have played a role[5]. This evidence concerns the gene BRCA1 and breast cancer.