BRCA1 and breast cancer: BRCA1 mutation carriers have a big risk of early onset developing breast cancer with a lifetime risk of 56% to 84% and the estimated risk of developing ovarian cancer in BRCA1 mutation carriers ranges from 36% to 63%, whereas BRCA2 mutation carriers have an increased risk for both breast and ovarian cancer with an estimated risk of ovarian cancer ranging from 10% to 27%.