Most breast cancers are not caused by inherited cancer genes, and most people who develop breast cancer don’t have a strong family history of it.
But sometimes breast cancer can run in families. In general, the chance of there being a family link is greater when:
- a number of family members have been diagnosed with breast cancer or related cancers, such as ovarian cancer
- the family members are closely related
- the family members were diagnosed at a younger age.
Inherited genes and breast cancer
Less than 1 in 10 breast cancers are thought to be caused by a change (alteration) in a gene running in the family.
The two genes most often found to be altered in hereditary breast cancer are called BRCA1 and BRCA2.
If a family has an altered BRCA1 or BRCA2 gene, usually several relatives on the same side of the family may be diagnosed with breast cancer or related cancers. People in the family may also be diagnosed with cancers at a particularly young age.
BRCA gene alterations are more common in certain populations. If you have Ashkenazi Jewish ancestry and have relatives who’ve been diagnosed with ovarian or breast cancer, you may want to discuss your risk with your GP.
If you are concerned about your risk of breast cancer, talk to your GP. They can talk to you about your family history and your risk.
Assessing family history
A family history of cancer is usually based on your close relatives, including first-degree relatives.
First-degree relatives are your parents, brothers, sisters and children.
Close relatives are your first-degree relatives and second-degree relatives (grandparents, grandchildren, aunts, uncles, nieces and nephews).
You may have an increased risk of developing breast cancer if your family history includes:
- one first-degree relative who developed breast cancer under the age of 40
- one first-degree male relative (father, brother or son) who developed breast cancer at any age
- one first-degree relative with cancer in both breasts when the first cancer was diagnosed under the age of 50
- two first-degree relatives who developed breast cancer at any age
- a first-degree relative and another close relative on the same side of your family who developed breast cancer at any age
- three close relatives on the same side of your family who developed breast cancer at any age
- close relatives with breast and ovarian cancer on the same side of the family.
If any of these apply to your family, or you are worried about your risk, talk to your GP. They may be able to reassure you, or refer you to a clinical genetics service or family cancer clinic.