If a woman's sister, mother, or another close relative has had breast cancer, the woman may have an increased risk of getting the disease herself. Hereditary breast cancer makes up 5 to 10 percent of all breast cancer cases. The genes in cells carry the hereditary information that is received from a person's parents. Several genes have been found to be defective in some breast cancer patients. Relatives of breast cancer patients who carry these defective genes may be more likely to develop breast or ovarian cancer.
Some defective genes are more common in certain ethnic groups.
Tests are being developed to attempt to identify the genetic defect long before any cancer appears. Some other risk factors include early onset of menstrual periods, late menopause, having a first child after age 30 or never having children, and having ovarian cancer, endometrial cancer, or previous breast cancer. This information is not intended to be a substitute for individual medical advice in diagnosing or treating a health problem. Please consult with your health care provider about your health care concerns.