The risk of developing breast cancer is twice as high in women who have an affected first-degree relative (FDR) than women in the general population.
The majority of the genetic risk is due to low-risk or moderate-risk susceptibility alleles, each
of which confers only a very small increased risk in isolation but which in combination may have quite a significant effect.1
Currently these low-penetrance genes cannot be used clinically in the management of individual patients but they may, in time,be helpful in the context of population screening programmes for
disease prevention.
Pathogenic variants in high-penetrance genes such as BRCA1 and BRCA2(Table 1) confer a high risk of breast cancer, but these variants are rare and only account for a small percentage of breast cancers.