Information for Health Professionals is also available.
Most cancers are not due to a hereditary (inherited) risk. While anyone can get cancer, some kinds of cancer are seen more often in some families. This may be related to factors that are shared in a family such as diet, smoking, or environmental exposures. Research has identified specific genes linked to a few specific patterns of cancers in some families. Other genes will be identified in the future.
Does cancer run in my family? is a pamphlet that gives more information. 
Does my family have a higher risk of cancer?
Because cancer is quite common, and there are so many types of cancer, almost everyone has some history of cancer in their family. In large families it is not unusual for several relatives to have some kind of cancer. A family history of cancer may increase your risk of developing cancer. For example, if one or two women in your family had breast cancer before age 50, you may be twice as likely to develop breast cancer as a woman of your age with no family history of breast cancer.
Only 5-10% of all cancers are related to an inherited gene mutation. In those cases, a specific gene mutation may be passed down in a family, from a parent to a child. Each child in such a family has a 50-50 chance of inheriting the gene mutation. Inheriting the gene mutation does NOT mean that the child is born with cancer. It means that the child has a higher risk of developing cancer sometime during his/her life. Because many genes are involved in cancer formation, not everyone who inherits a gene mutation will develop cancer.
Most family histories of cancer are NOT related to an inherited gene mutation.
A family history that might indicate an inherited gene mutation would include two or more of the following points:
- cancer in several closely related people, on the same side of the family, in several generations
- cancer at younger ages than usual (e.g., breast cancer in the 30s)
- more than one diagnosis of cancer in the same person
- specific types of cancer that are linked to specific genes (e.g. breast cancer & ovary cancer, or colon cancer & endometrial cancer)
If the points above do not describe your family, it is very unlikely that the cancer in your family is due to an inherited risk.
What can I do if I think my family has a higher risk of cancer?
If the points above describe your family history, bring this to your doctor's attention. Careful screening may help with early detection of any cancer that might develop. A detailed review of your family history by genetics experts may also be valuable.This can occur through a referral to the Hereditary Cancer Program.
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Updated February 12, 2010