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 < or = 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.