Cancer Genetics: Focus on BRCA1 and BRCA2 Mutations

What is Cancer Genetics?

Cancer genetics is the study of how individuals' personal and family history may increase their risk for certain cancers. Cancer genetics is becoming an important part of understanding the complex disease of cancer and the role that inheritance may play.

Cancer may be caused by many things, such as exposures to chemicals in our environment, behaviors like smoking and the genes we inherit from our parents. In most cases cancer is likely the result of a complex interaction between all of these things.

The genes we inherit from our parents are part of what might increase our risk for certain cancers. If the genes we inherit carry unexpected changes known as mutations that might put a person at a higher risk for cancer. For example, mutations in the genes called BRCA1 and BRCA2 put a person at a higher risk for breast and ovarian cancer.

Genetic causes of cancer are not common. Recently genetic tests have been advertised as a way for people to find out if they are at risk. These tests are often done by taking a sample of a person's blood. Although these tests may be helpful to some people, they are not meant for everyone. It is important to talk directly to a doctor or a genetic counselor to help you decide whether genetic testing is right for you.

To help you understand cancer genetics, the following sections will focus on one example of a genetic cause of cancer: BRCA1 and BRCA2.


One genetic test that is commonly promoted to the public is the test for BRCA1 and BRCA2 gene mutations. Mutations in either of these two genes are tied to cases of inherited breast and ovarian cancer.

BRCA1 and BRCA2 mutations can be inherited from either your mother or your father. These mutations are not common in the general population. Five to 10 percent of all breast cancer cases, and up to 15 percent of ovarian cancer cases, are thought to be caused by BRCA1 and BRCA2 mutations.

Genetic counseling can help women and men who may be at higher risk for a BRCA1 or BRCA2 mutation to understand their risk. Genetic counseling is an important part of deciding whether genetic testing is right for you.