The exact cause of breast cancer — that is, what causes breast cells to start to grow out of control — is not known. The combination of a person's genes and their environment likely plays a role in the development of the disease.
In about 5 to 10 percent of Breast Cancer cases, genetic mutations are linked to the disease. For example, women with mutations in the BRCA genes are at increased risk for breast cancer. Some studies show that women with mutations in the BRCA1 gene have a 50 percent to 70 percent chance of getting breast cancer by age 70, and women with mutations in the BRCA2 gene have a 40 percent to 60 percent chance, a nonprofit organization that funds breast-cancer research and advocates for patients.
Risk Factors of Breast Cancer
1. family history of breast cancer,
2. starting menstrual periods before age 12 or going through menopause after age 55,
3. not having children,
4. having dense breast tissue,
5. using hormone therapy after menopause,
However, most women who get Breast cancer don't have any risk factors for the disease, other than their gender and age, the ACS says.