Some genes have mutations or mistakes, which means that they do not perform properly. Such mutations are very common. Almost everyone has some form of abnormal genes in some of the cells of their body. Mutations can either be inherited or occur during the course of a person's lifetime. Although most mutations are harmless, some can increase your risk of developing certain diseases, such as breast cancer.
In the past few years, research has indicated the presence of a specific gene mutation in some families with a history of breast cancer. These abnormalities are often found in genes named BRCA1 and BRCA2 (BReast CAncer gene 1 and BReast CAncer gene 2). Although the normal version of these genes do not harm its carrier, the abnormal BRCA1 and BRCA2 genes are associated with higher rates of breast and/or ovarian cancer. BRCA1 and BRCA2 abnormalities are found in about 5% to 10% of breast cancers.