Hereditary breast cancer.

Information on genetics is in process of exponential growth, with a corresponding recognition that most medical information, screening and diagnostic tests, and disease processes have a genetic component. Hereditary breast cancer is a good example, showing the complexity of cancer genetics in a clinical context. The contribution of family history to the risk of developing breast cancer has been appreciated for some time. Breast cancer was believed to be a result of multiple genetic and environmental factors. Today it is known that single genes are also responsible for breast cancer and some of these genes (BRCA1 and BRCA2) can be identified by genetic testing. Genetic information on breast cancer is, however, still limited and although the tests that are now available can be beneficial, they also carry some risks and limitations.