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In a small number of cases, breast cancer runs in the family. Of all women who develop breast cancer, about one in five has a significant family history of the disease.
If there is a history of breast cancer, or some other cancers (especially ovarian cancer) in your family, this may increase your risk of developing the disease, and possibly at a younger age. It doesn’t, however, mean that you’ll definitely get breast cancer. We can’t always say what causes breast cancer or predict who will develop it, but a combination of our genes, lifestyle and life choices and surrounding environments can play a role.
Most cases of breast cancer are not hereditary and occur when there is either no family history or only one case in an older relative, which would be expected to occur by chance.
Genetic faults associated with breast cancer
The cells in our bodies each contain thousands of genes, which we inherit from our parents. These provide instructions to tell our cells how to function. People who have inherited faults in known breast cancer genes – such as BRCA1 or BRCA2 – have an increased risk of developing breast cancer.
Women with a particularly strong family history have a high risk of breast cancer and could have inherited BRCA1 or BRCA2 faults that run in their family. These faults can sometimes be identified through genetic testing.
About 10,000 women diagnosed with breast cancer each year will have a family history of the disease. Of these, around a quarter – or 2,500 patients each year – will have inherited faults in known breast cancer genes, eg BRCA1 and BRCA2.
A further 5,000-7,500 people each year are believed to be affected by other genetic factors linked to breast cancer, but the specific genes involved are not yet known in many cases.
Information last reviewed: 12 August 2013