This is in line with our results, that is, a risk for contralateral breast cancer of 15.7% (95% CI 9.7% to 21.7%) after 5 years and 33.4% (95% CI 24.6% to 42.1%) after 10 years for women from BRCA1 positive families that developed the first breast cancer before the age of 35 years. This evidence concerns the gene BRCA1 and breast cancer.