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Gene mutations that are passed down from your mother and/or father can increase hereditary risk of breast cancer, so what do we know about these genes, and how do they affect risk?

The most widely recognised mutations associated with breast and other cancers are in the BRCA1 and BRCA2 genes, but other mutation sites, such as TP53, PTEN and STK11 have been identified. These genes encode for proteins called tumour suppressor proteins that check for errors and help repair DNA during growth and tissue repair as part of the normal cell division process.

When a mutation is present in these genes, the tumour suppressing protein may not be made at all, or does not perform very well as part of the error checking and repair team. This can result in errors being missed when new DNA is being made as a cell divides. If errors accumulate, cancer can occur.

People that inherit these gene mutations have an increased risk of breast, ovarian, and possibly other cancers too, but having a gene mutation does not mean you will definitely get cancer. Indeed, specialists believe that hereditary factors account for less than 5% of breast and other cancers.

In the UK, you are eligible for genetic testing if you have already have a family member who has tested positive, have 2 or more close family members on the same side of the family who have been diagnosed with breast and/or ovarian cancer, or have family members who received a cancer diagnosis when they were below the age of 50.

We are learning more about the genetics of cancer each year, and although blood tests do exist for some gene mutations such as BRCA1 and 2, we do not have blood tests yet for all of the hereditary mutations currently known, and we still have more to identify.