Breast Cancer Causes
In most cases of breast cancer, the cause is not known. Research scientists believe that heredity plays a role in approximately 5 to 10 percent of cases. While not "causes," certain risk factors can increase a person's chance of developing breast cancer. These include a family history of the disease, dense breast tissue, and early menstruation.
Scientists are not sure of the breast cancer causes in most cases of the disease. In 5 to 10 percent of breast cancer cases, there is a genetic reason for the breast cancer.
The genes in cells carry the hereditary information that is received from a person's parents. As mentioned, hereditary breast cancer makes up approximately 5 to 10 percent of all breast cancer patients. Some altered genes related to breast cancer are more common in certain ethnic groups.
Women who have an altered gene related to breast cancer and who have had breast cancer in one breast have an increased risk of developing breast cancer in the other breast. These women also have an increased risk of developing ovarian cancer, and may have an increased risk of developing other cancers. Men who have an altered gene related to breast cancer also have an increased risk of developing this disease.
Tests have been developed that can detect altered genes. These genetic tests are sometimes done for members of families with a high risk of cancer.
(Click Breast Cancer and Genetics, Breast Cancer Screening, or Breast Cancer Prevention for more information.)