BRCA1 and breast cancer: In a retrospective study of 6230 women from high risk families, with or without a known BRCA1/2 mutation, Rhiem observed a cumulative contralateral breast cancer risk, 25 years after a first breast cancer diagnosis of 44.1% (95% CI 37.6–50.6) in BRCA1 positive families, 33.5% (95% CI 22.4–44.7) in BRCA2 positive families and 17.2% (95% CI 14.5–19.9) in BRCA1/2 negative families [56].