There are several gene mutations that increase a woman's risk of getting breast cancer. The most common are BRCA1 and BRCA2. They are responsible for only 5 percent to 10 percent of all breast cancers, but having one dramatically increases your risk.

On average, one out of eight women will develop breast cancer. Having BRCA1 increases the chance of developing breast cancer up to 85 percent; having BRCA2, up to 65 percent.

Patterns of cancer in your family history are the best indicators. Red flags include having a female relative with breast cancer at an early age, a male relative with breast cancer, a family member with breast cancer in both breasts, a female relative with ovarian cancer, a second cancer in a relative with breast cancer and family members with other cancers — particularly ovarian, prostate and pancreatic cancers and melanoma.

Testing for BRCA1 and 2 involves a simple blood draw, yet the test can cost a few thousand dollars, and it is not covered by all insurance plans. If the test reveals that you have one of the genes, you may need to get mammograms or breast MRIs more often. Preventative options include medications like tamoxifen and raloxifene.

Most breast cancers are not hereditary. Women at average risk should get annual breast exams and do monthly self-exams starting in their early 20s. Yearly mammograms should begin by age 40.

Dr. Carrie C. Morrison is director of breast imaging and mammography at St. Luke's Hospital. Call 314-205-6491 or visit stlukes-stl.com. XX Files, a women's health column, rotates each week with Aging Successfully, a column for seniors by Dr. John Morley of St. Louis University.