Understanding Hereditary Cancer

M. D. Anderson Cancer Center
Date: December 2008
Time: 04:27

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All cancers are due to changes in our genes. Genes are found in every cell of our body. Genes come in pairs – we get one from our mother and one from our father. Genes tell our cells what kind of tissue to become, when and how to grow more cells, or when to repair damage to our cells. Some genes regulate or prevent cancer growth. If one of these genes changes, it can increase your chances for developing cancer. When a gene is changed, we call that a mutation.

An easy way to understand genes and mutations is to think of baking a cake. We use a recipe to tell us how to make the cake. It tells us how much of each ingredient to use and what steps to follow. Genes are like recipes for our cells. If the recipe is altered or changed, let’s say we accidentally use one cup of baking soda instead of one tablespoon of baking soda, we wouldn’t get the same result. In fact we’d have a big bubbly mess on our hands. This change to the recipe is like a mutation.

So when genes change or mutate, cells can grow out of control and cause cancer.

Gene mutations that lead to cancer usually occur later in life, as we age and are exposed to things like smoke or environmental carcinogens, hormones, certain viruses or as a result of dietary factors, such as drinking alcohol or eating a high-fat diet. If cancer occurs due to these types of mutations, it is called sporadic cancer.
However, sometimes people are born with gene mutations that cause cancer. This is called hereditary cancer.

Cancer is a common disease. This year more than a million Americans will be diagnosed. Most cancers occur in people over the age of 55. Half of all men and a third of all women will be diagnosed with cancer at some point in life. Contrary to popular belief, 90 percent of cancers are thought to be sporadic and only five to 10 percent of all cancers are hereditary.

Hereditary cancers have some important characteristics in common. They usually occur at an earlier age. As a result, screening exams and risk reduction recommendations may be different and may need to begin earlier. In families with hereditary cancers, multiple family members may have the same or similar cancers, and they may occur across several generations. Also, cancer is more likely to develop in more than one site in the body. And finally, rare cancers may occur, such as male breast cancer.

Hereditary gene changes also can be passed on to children. Each child has a 50 percent chance of inheriting the mutation. If you have hereditary cancers in your family, you may be at risk for more than one kind of cancer, or if you’ve already been diagnosed with cancer, this may impact your treatment or follow-up care.

Most inherited gene mutations are labeled as genetic syndromes. Syndromes for breast, ovarian, colorectal and endometrial are the most common.

The most common type of inherited breast cancer is caused by hereditary breast and ovarian cancer syndrome. In this syndrome, there are mutations in the BRCA1 and BRCA2 genes. A woman with an inherited mutation in the BRCA genes is at an increased risk of developing breast and ovarian cancer compared to a woman who does not carry the mutation. A man with an inherited mutation in the BRCA genes also is at an increased risk of developing breast and prostate cancer. Additionally, some affected families have a higher incidence of other cancers, such as pancreatic cancer and melanoma.

Hereditary nonpolyposis colorectal cancer syndrome, or Lynch Syndrome, is another genetic syndrome that puts people at an increased risk for developing cancer. People with this syndrome can develop colorectal and endometrial cancers at an early age. Other variations of this syndrome are associated with increased risk for certain skin or brain tumors.

Familial adenomatous polyposis, sometimes called FAP, is another colon cancer syndrome in which hundreds to thousands of precancerous colon polyps develop throughout a person’s gastrointestinal tract. This puts them at an increased risk of colorectal cancer. Additionally, individuals with FAP have a higher chance to develop desmoid tumors, thyroid cancer and other benign conditions.

Some other hereditary cancer syndromes you may have heard of include Cowden syndrome, Li-Fraumeni syndrome, Von Hippel-Lindau disease and multiple endocrine neoplasia. To learn more about these syndromes, visit our web site.

Even though hereditary cancer syndromes significantly increase your risks for cancer, it’s important to remember that only 5 to 10 percent of cancers are considered hereditary. Also, it’s important to remember that not all gene mutations, inherited or otherwise, lead to cancer.

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