BRCA1 and breast cancer: The question of how to deal with incidental findings is typically important when dealing with rare genetic variants (i.e. genetic variants with a low frequency in the population under study but high estimated risk of disease) or mutations in genes that are known to have a major impact on the development of a disease (e.g. genetic mutations in the breast cancer genes BRCA1 and BRCA2 usually have a major influence on the development of breast cancer).