While cancer is not inherited, the genes you receive from your parents may affect your chances of developing certain cancers. Cancers may also appear to run in families due to similar risk factors, including shared habits, like tobacco or alcohol use, or a shared environment, like exposure to air pollution. Inherited genetic mutations in cancer-related genes can also increase your cancer risk. These genetic changes cause hereditary cancer syndromes, also known as family cancer syndromes.

How Do Genetic Mutations Cause Cancer?

Every cell in your body has a copy of your genes, which act as an instruction manual for how the cell should function. Genes are a part of your DNA, and your DNA tells the cells in your body how quickly to grow, how often to divide, and how long they live. Cancer occurs when a change is made to your genes, which affects the way the cells grow and multiply. This change may occur randomly as the cell naturally divides, because of exposure to cancer causing substances in your environment, or it may be inherited from your parents.

Cells that change randomly or due to environmental factors cannot be passed down from parent to child. For a genetic change to be inherited, the mutation must be present in a parent’s egg or sperm cells. Up to 10 percent of all cancers may be caused by inherited genetic changes—this is why cancer can appear to run in families.

Hereditary cancer syndromes are a type of hereditary disorder caused by these mutated genes. A person with these syndromes will have a higher-than-average chance of developing the cancer associated with that genetic mutation. They may also develop other noncancer health conditions.

What Types of Cancer Are Caused by Hereditary Cancer Syndromes?

There are many kinds of genetic mutations, and many hereditary cancer syndromes. The two most common types are:

Hereditary Breast and Ovarian Cancer Syndrome

Hereditary Breast and Ovarian Cancer (HBOC) syndrome is linked to increased risk for breast cancer and/or ovarian cancer. Women with this syndrome may develop cancer at a younger age than the average onset. Men with this syndrome also have an increased risk of breast cancer and other associated cancers, including prostate cancer, melanoma, and pancreatic cancer. HBOC is commonly linked to genetic changes in the BRCA1 and BRCA2 genes but may also occur because of mutations in the TP53, PTEN, CDH1, ATM, CHEK2, or PALB2.

Lynch Syndrome

Lynch syndrome, also known as hereditary non-polyposis colorectal cancer, is the most common inherited syndrome that increases risk for colon cancer. People who have inherited Lynch Syndrome are more likely to develop colorectal cancers before the age of 50. They may also have a high risk of endometrial, stomach, liver, kidney, brain, and skin cancer. Lynch syndrome is caused by mutations in the genes that effect DNA mismatch repair—a process that fixes mistakes in copied DNA. Normally, these genes protect you from certain cancers, but a mutation may keep them from working properly.

Do I Need Genetic Testing?

Predictive genetic testing looks for these inherited gene mutations to determine if a person may be at a higher risk for developing certain kinds of cancer. Most people do not need genetic testing, but it may be recommended for people who had certain cancers and/or patterns of cancer in their family. Genetic testing may be recommended if you have:

• Several immediate family members with cancer
• Many relatives on one side of your family with the same type of cancer or related cancers
• Family members with cancer potentially linked to a gene mutation
• Diagnosis of some types of cancer at a younger than average age
• A known hereditary cancer syndrome in your family

If you have a concern about your family health history, talk to your physician to determine whether genetic testing makes sense for you.

It is recommended to see a genetic counselor about genetic testing. They will discuss which genetic test is best for you. Once testing is complete, the genetic counselor and your physician will help you understand your risk and the next steps to take for your health.

Learn More About Hereditary Cancer Syndromes and Genetic Testing

Understanding your—and your family’s—cancer risk can go a long way in protecting your health. Speak to a physician about any concerns you may have.