Familial Adenomatous Polyposis

Cancer risk with familial adenomatous polyposis

The major cancer risk in FAP is cancer in the large and small intestines. For people with classic FAP, Gardner syndrome, and Turcot syndrome, polyps in the colon often start appearing around age 16. They can appear as early as 7 years of age or as late as 35.

By age 35, about 95% of people with these conditions have developed polyps in the colon. Without surgery to remove the colon, people with these types of FAP will all eventually develop colon cancer. The average age of colon cancer in people with FAP who have not had their colon removed is 39.

Up to 1 in 8 people with classic FAP, Gardner syndrome, and Turcot syndrome are also at risk for small intestine cancer. Small intestine cancer usually occurs after age 17. The average age of diagnosis is 45–52 years.

People with attenuated FAP have a slightly lower risk of colon cancer compared to classic FAP. For those with this subtype who have not had their colon removed, the average age of colon cancer diagnosis is 50–55.

Familial adenomatous polyposis signs

Other features of FAP include:

• Polyps (growths) in the colon and rectum
• Blood in stool
• Teeth that are extra, missing or do not emerge from the gums
• Dark patches on retina of the eye present from birth
• Skin cysts or tags 
• Bony growths on the legs, arms, or head
• Non-cancerous soft tissue tumors in the abdomen
• Non-cancerous tumors of the adrenal glands
• Rarely, a type of liver cancer called hepatoblastoma

Causes of familial adenomatous polyposis

Genes carry information telling cells in the body how to function. FAP is caused by changes in the gene APC. This gene helps control how cells grow and divide.

How familial adenomatous polyposis is inherited

Most people without FAP carry 2 working copies of the APC gene in their cells. One copy is from their mother. Another copy is from their father. Cells from people with FAP carry 1 working copy of APC and 1 copy that is changed. This change causes the gene to not work right. It is called an APC mutation.

Most children with FAP inherit the APC gene mutation from a parent who also has FAP. About 20–25% of people with FAP have a new APC mutation that did not come from a parent. These children have no history of FAP in their family. In these cases, the change happened in either an egg or a sperm or in a cell of the developing embryo. These children are the first in their families to have FAP.

No matter how the APC gene changed, people with FAP have up to a 50% (1 in 2) chance of passing it on to their children.

As people with FAP get older, the remaining working copy of APC often changes within some of their cells. When both copies of the gene change, polyps and eventually cancer can develop. That is why people with FAP have a higher risk of developing cancer than people who do not have FAP.

Learn more about genetic counselors and understanding genetic risk.

Diagnosis of familial adenomatous polyposis 

Health history

A health care provider may suspect that your child has FAP after studying their medical and family cancer history.

This information helps the health care provider and the genetic counselor know if:

• There are more cancers than normal in your family
• These cancers occurred at younger-than-expected ages
• The types of tumors and other signs and symptoms are those that are seen in FAP

Your provider or genetics counselor may recommend genetic testing if they suspect FAP.

Learn more about types of genetic tests.

Genetic testing for FAP

A blood sample is sent to a genetic testing lab. The lab runs genetic tests that looks for changes in the APC gene.

If your child has an APC mutation, the genetic counselor will work with your family to:

• Find out if other family members should consider testing for an APC mutation
• Help your family understand the increased cancer risk from FAP
• Give you information to help with your decisions about prenatal genetic testing

Genetic testing before or during pregnancy

Parents may choose to do prenatal testing to find out if a pregnancy is affected with a known APC mutation. Testing may take place either before pregnancy occurs or during pregnancy.

You should work with a genetic counselor to review the pros and cons of the test. The genetic counselor can also help you prepare for the test results.

Testing before pregnancy is called preimplantation genetic testing (PGT). This special type of genetic testing is done along with in vitro fertilization (IVF). PGT tests embryos for a known APC mutation before a provider places them into the uterus.

Testing during pregnancy can help providers see if a pregnancy is affected with a known APC mutation. A provider gathers cells from the pregnancy in 1 of 2 ways:

• Chorionic villus sampling (CVS) is done during the first trimester (first 3 months).
• Amniocentesis is done during the second trimester or later (last 6 months).

After tissue collection, the lab checks the sample for the APC mutation. Both tests carry minor risks. Discuss these risks with an experienced health care provider or a genetic counselor.

Special concerns for genetic testing

Take time to think carefully about the benefits and risks of genetic testing. Speak with a genetic counselor before testing. If you decide to get tested, talk with your health care provider or a genetic counselor about your results so you can understand what they mean.

Sometimes, children or adults with FAP feel sad, anxious or angry after getting their test results. Parents may feel guilty if they pass the APC gene mutation to 1 or more of their children. People with an APC gene mutation may also have trouble getting disability or life insurance.

Read more about genetic discrimination.

Monitoring and follow-up care for familial adenomatous polyposis

To manage FAP, it is important to get regular screening for polyps. If polyps are found, they are removed. If there are many polyps, the colon may eventually be removed. The goal of screening is to find and treat growths such as polyps or other tumors early for the best outcome.

Cancer screenings for children with FAP

• Yearly physical exams by a health care provider who knows FAP well.
• Ultrasound exams should be used to screen for liver cancer. These start when the child is an infant. They are repeated every 3 months until age 4 years.
• A blood test should be done to check the levels of alpha-fetoprotein (AFP), a protein that is released by liver cancer cells. Checking a child’s levels of AFP in the blood can help screen for liver cancer. This test begins when the child is an infant. They are repeated every 3 months until age 4 years.
• Sigmoidoscopy or colonoscopy help health care providers find polyps and cancer in the large intestine. In both procedures, a small camera allows a health care provider to look inside the intestine. A colonoscopy examines the entire large intestine. A sigmoidoscopy focuses on a shorter portion of the large intestine. These procedures start at age 10–12 years or 5–10 years before the earliest intestinal cancer diagnosis in the family. These tests are repeated every 1–2 years.
• Esophagogastroduodenoscopy (EGD) uses a small camera to look for polyps and cancer in the upper part of the digestive system. EGD is done before the colon is removed. If the colon is not removed, it is done by age 25 or starting at 5–10 years before the earliest age of small bowel cancer in the family.
• A thyroid exam should begin in the late teens. It should be repeated every year. A provider may also do an ultrasound exam of the thyroid every year.
• A baseline brain MRI may be considered for families with a history of medulloblastoma or other brain tumors.

Cancer screenings for adults with FAP

• Yearly physical exams by a health care provider who knows FAP well.
• A thyroid exam should be done every year. Some health care providers may recommend an ultrasound exam of the thyroid every year.
• A sigmoidoscopy or colonoscopy should be continued as suggested by a gastroenterologist (GI doctor).
• An EGD should be done before the colon is removed, beginning by age 25, or starting 5–10 years before the earliest age of small bowel cancer in the family. How often EGD is repeated depends on the results of the first exam.
• A baseline brain MRI may be considered for families with a history of brain tumors.

Cancer screenings for attenuated FAP

Screenings for attenuated FAP are different than for other forms of FAP. Recommended screenings may change over time as doctors learn more about FAP and all of the subtypes. Talk about all screening options with your care team. Because FAP is a complex condition, seek out an experienced doctor for your child.

Living with familial adenomatous polyposis

People of any age with FAP have a higher risk of cancer. It is important to monitor children’s health and help them adopt healthy habits. They need to have regular physical checkups and screenings. That way, the care team can find cancer early at the most treatable stage.

Problems to watch for

People with FAP should watch for signs or symptoms that could signal cancer, such as:

• Unexplained weight loss
• Appetite loss
• Pain in the stomach or abdomen
• Blood in the stool or changes in bowel habits
• Aches, pains, lumps, or swelling for no clear reason
• Headaches or changes in vision or nerve function that do not go away

It is important to seek medical help if anything unusual appears.

Maintain a healthy lifestyle

Habits that will help you maintain a healthy lifestyle include:

• Eat a healthy diet with lots of fruits and vegetables.
• Get regular exercise
• Avoid smoking or using tobacco products.
• Avoid secondhand smoke.
• Avoid excess sun exposure. Always wear sunscreen, a hat, and protective clothing when in the sun.

Familial adenomatous polyposis care at St. Jude

The St. Jude Cancer Predisposition Program is dedicated to diagnosing and screening children with a genetic predisposition for cancer. Our program offers the best clinical care possible. We engage in cutting-edge research to gain more information about genetic disorders and cancer, and to improve the care and treatment for patients who are affected by these conditions. Learn more about the Division of Cancer Predisposition at St. Jude.

Our genetic counselors, clinicians, genetics nurse practitioners, and research assistants work together to provide patients with:

• A complete health history
• A record of cancer that happened over the past 3 generations (family tree or pedigree) to see how diseases were passed down
• Physical exams to check for genetic disease
• Confidential genetic counseling and testing
• Cancer screenings for those with genetic disease to detect and treat cancer as soon as it occurs
• Recommended cancer treatments and ways to reduce cancer risk
• Genetic testing for immediate (1^st degree) relatives

FAP increases your child’s risk for many types of cancer. 

If you have questions about the Genetic Predisposition Clinic and care for FAP, email our team at GPTeam@stjude.org.

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