Just as family members can share physical traits, such as eye and hair color—as well as height, they also can share a tendency to develop cancer. About 5 percent to 10 percent of cancer cases are due to unusual changes in certain genes—more commonly called "genetic mutations"—that run in families. Normally, the affected genes work to keep the body's cells healthy, but when there is a mutation, they lose that ability.
Certain types of cancer can, in a relatively small number of cases, be linked to family history. Examples include the following:
- Breast cancer
- Ovarian cancer
- Colorectal cancer
- Prostate cancer
- Thyroid cancer
- Melanoma (a type of skin cancer)
For many of these cancers, researchers have been able to identify—and test for—the genetic mutations that make people more susceptible to them. People who inherit the mutation (or mutations) are significantly more likely than members of the general population to develop cancer.
For example, women with mutations in genes known as BRCA1 and BRCA2 have a greatly increased risk of breast and/or ovarian cancer.
- Although about 13.2 percent of women in the general population will develop breast cancer in their lifetimes, anywhere from 36 percent to 85 percent of women with a BRCA mutation will develop the disease.
- Less than 2 percent of women overall can expect to get ovarian cancer, but among women with a BRCA mutation, anywhere from 16 percent to 60 percent will get it. (The range is due to different findings from different studies.)