BRCA1 and ovarian cancer: However, when there are mutations in the BRCA1 and BRCA2 genes, the risk of breast cancer increases considerably to 46–87% for mutations in the BRCA1 gene and 38–84% for mutations in the BRCA2 gene; in addition, the risk of ovarian cancer is 39–63% for mutations in the BRCA1 gene and 15.5–27% for mutations in the BRCA2 gene.