BRCA2 and breast cancer: Meta-analyses have indicated a mean cumulative breast cancer risk at age 70 years of 57% (95% CI: 47%-66%) for patients carrying the BRCA1 mutation and 49% (95% CI: 40%-57%) for patients carrying the BRCA2 mutation.150 ER positive tumors account for ∼10%-36% of breast cancers that occur in BRCA 1 mutation carriers,151 compared with 70%-80% of BRCA 2-associated breast cancers.152