Genetics
Approximately 5 to 10 percent of cases of breast cancer are inherited. Alteration carriers in either of two genes, named BRCA1 or BRCA2. Women with an inherited BRCA1 gene alteration have a 72 percent chance of developing breast cancer by the time they are 70. There is a 69 percent chance that by 80, a woman with an inherited alteration in the BRCA2 gene will get breast cancer.