What is the role of genetics in breast cancer?

Lynn Hartmann, M.D., Oncologist; Director, Ovarian Cancer Program, Mayo Clinic Cancer Center

Question: What is the role of genetics in breast cancer?

Answer: It's been known for centuries that there is a hereditary process underlying some breast cancers. It was described back in Roman times. Right now we know that about 15-20 percent of women who are diagnosed with breast cancer have some family history of breast cancer. Now, that can be a very dramatic family history where multiple relatives have breast cancer at an early age. That we call "hereditary" -- meaning there's a gene traveling through the generations in this family that is causing this unique susceptibility. That probably is present in about 5 percent of breast cancers. The more common family history is: my aunt had breast cancer when she was 70, because it is a common disease. So there's two levels of involvement of genetics here -- the true hereditary process, not very common but certainly very striking when it's present; the more common, but less dramatic, slight family history, and both of those are included when we say, the role of genetics in breast cancer.