Hereditary cancer, or inherited cancer, is cancer that occurs as a result of a genetic change (mutation) that a person is born with. All cancer is a result of genetic changes that cause a cell to divide faster than it should. These changes can occur in a gene that slows down cell division, in a gene that speeds up cell division, or in a gene that is in charge of repairing genetic changes. These are collectively known as cancer susceptibility genes. People have two copies of these genes in all of their cells.
As a person ages and gets exposed to different things in the environment, such as smoking or the sun, their genes are changed (acquired mutations). Most cancer occurs because both copies of a person’s cancer susceptibility gene get changed over time (sporadic cancer). In hereditary cancer, a person is born with a change in one copy of a cancer susceptibility gene. This significantly increases their lifetime risk of cancer because it is more likely, and takes less time, to get a change in the one remaining unchanged gene copy.
About 10% of all cancer is hereditary and there are many types, depending on the gene that is affected. The most common forms of hereditary cancer are breast cancer, ovarian cancer, and colorectal cancer. Factors that increase the risk of cancer being hereditary include multiple family members affected with similar types of cancer, cancer at a young age (less than 50 years) in the family, rare forms of cancer in the family (such as kidney cancer or breast cancer in a man), and more than one type of primary cancer in a person (a woman with both breast and ovarian cancer). If you have signs of hereditary cancer in your family, talk with a genetic counselor about the likelihood of it being hereditary as well as genetic testing options. Diagnosing hereditary cancer in a family can help to determine a person’s cancer risk as well as determine cancer surveillance recommendations.