Within a family if a high number of close relatives developed cancer at a young age a person is said to have a family history of breast cancer. If breast cancer has affected a high number of relatives this is known as familial or hereditary breast cancer.
This type of breast cancer is believed to be caused by a faulty gene. Only about 5-10% of incidents of breast cancer are due to an inherited factor. People from an ethnic background - for example Ashkenazi Jewish ancestry - where a faulty gene is present may have an increased risk of developing breast cancer. For the majority of people age is the greatest risk factor.
Three main genes have been linked to breast cancer, and these are as follows:
- BRCA1 (breast cancer 1)
- BRCA2 (breast cancer 2)
- TP53 (tumour suppressor protein 53)
The chances of developing breast cancer increase if a person is found to have a fault in either BRCA1, BRCA2 or TP53. Remember this increases the risks but does not necessarily mean that a person will develop breast cancer.
If a parent carries a faulty gene they will also carry a normal copy of the gene. This means that any offspring will have a 50:50 chance of inheriting the faulty gene and also a 50:50 chance of inheriting the normal gene. Only if a person inherits a faulty gene do they have a 50:50 chance of passing this fault on to their offspring. If a person does not inherit a faulty gene then they cannot pass on the faulty gene to any children they may have.
It has been found that for people that carry a faulty BRCA1 or BRCA2 gene they are at an increased risk of developing ovarian cancer. There is also an increased risk of developing other cancers if a person has a faulty BRCA2 gene.
For men that carry a faulty BRCA1 or BRCA2 gene it has been found that they have an increased risk of developing prostate cancer. For men that carry a faulty BRCA2 gene have been found to have an increased risk of developing breast cancer.
More rare types of cancer have found to be associated with the faulty TP53 gene, for instance cancers that develop in childhood.
Anyone concerned about their risk of developing breast cancer because of their family history should speak to their doctor for an assessment and advice.