BRCA1 and breast cancer: Women who have inherited mutations in BRCA1 or BRCA2 are at higher risk of developing breast and/or ovarian cancers.4 Risk increased with the number of affected women within the family, early age at diagnosis and the degree of relationship with other affected women.5–7 The cumulative risk of breast cancer by age 80 years was estimated to 72% for BRCA1 carriers and 69% for BRCA2 carriers.