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Genetics of Breast Cancer

Is Breast Cancer Genetic?

When cancer happens by chance or environmental exposures we call it “sporadic.”  About 75-80% of all breast cancers are sporadic. 

Some people may have a higher risk to develop breast cancer than others, due to their family history of breast cancer. 

Sometimes we see more breast cancers in a family than we would expect, but we aren’t exactly sure why.  These women are usually older (postmenopausal) when they are first diagnosed with breast cancer and typically there is not a history of other types of cancer in the family.  When we see families like this, we call it “familial” cancer.  About 15% of all breast cancers fall into this category.  These cancers may be caused by a combination of similar environments and exposures, or common genetic information.  Other women in the family may also have an increased risk to develop breast cancer. 

About 7-10% of breast cancer is caused by a genetic syndrome.  Individuals with genetic syndromes have a mutation (or change) in a gene that causes them to be at increased for breast cancer.  These mutations are inherited from either parent and can be passed on to children.  People with genetic cancer syndromes may be at risk to develop other types of cancers as well.  Learning if you have a cancer syndrome can help you understand your risk to develop cancer, your family’s risk to develop cancer, and potentially provide you with ways to reduce your cancer risk. 

What are examples of genetic syndromes that could cause breast cancer?

Hereditary Breast Ovarian Cancer Syndrome (BRCA1 / BRCA2)

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