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There are two types of a so-called gene for breast cancer: BRCA1 and BRCA2. Alterations in these genes tend to increase a person's risk for breast cancer, but not everyone with mutations in this gene will develop the disease.
Genes are nature's blueprints for every living thing. They come in pairs: one set of genes is passed down (or inherited) from your mother and the other set from your father. Genes determine how your body will function and grow, as well as the color of your hair and eyes, among other things.
Some genes do not function properly because there is a mistake in them. If a gene has a mistake, it is said to be mutated or altered. In fact, all people have altered forms of some genes. Some alterations can increase your risk for certain illnesses, such as cancer. In recent years, gene alterations have been found in some families with a history of breast cancer.
These alterations are most often found in genes named BRCA1 and BRCA2 (BReast CAncer Gene 1 and BReast CAncer Gene 2). Both men and women have these genes, so alterations in them can be passed down from either the mother or the father. It is likely that genes similar to these will be discovered in the future.
Altered Genes in Women
A woman with a BRCA1 or BRCA2 alteration is more likely to develop breast cancer than a woman without an alteration. However, not every woman who has an altered BRCA1 or BRCA2 gene will get the disease, because genes are not the only factor that affect a person's risk. Therefore, an altered gene by itself is not sufficient to cause cancer.
Most cases of breast cancer do not involve an altered BRCA1 or BRCA2 gene. At most, 1 in 10 cases involves an inherited altered gene, and not all inherited breast cancer involves BRCA1 or BRCA2.
Altered Genes in Men
Although breast cancer is rare, even in men with an altered gene, men with an altered BRCA2 gene have higher rates of breast cancer than men without an altered gene. Men with an altered BRCA1 or BRCA2 gene may also have a slightly increased risk of prostate cancer. Even if a man never develops cancer, he can pass the altered gene to his sons and daughters.
You can learn more about the breast cancer gene, genetic testing, and options by going to the eMedTV article Breast Cancer and Genetics.