BRCA1 and breast cancer: In the UK, however, mutations of these genes were detected in around 6% of women diagnosed with BC before the age of 36 years (3.5% in BRCA1 and 2.4% in BRCA2), while in women diagnosed between the ages of 36 years and 45 years, 4% had mutations in BRCA1 and 2% had mutations in BRCA2 [30].