Clinical Implications of Low-Penetrance Breast Cancer Susceptibility Alleles

Our understanding of breast cancer genetics is evolving beyond deleterious mutations in BRCA1 and BRCA2. In the past several years, several low- and moderate-risk breast cancer susceptibility alleles have been identified that have a relative risk for breast cancer of <= 2. The availability of new techniques such as genome-wide association studies ensures that more low- risk alleles will be identified. This article reviews our current understanding of low- penetrance genes, with a specific focus on their clinical implications.