How is familial adenomatous polyposis (FAP) diagnosed?

A doctor may suspect FAP when multiple adenomatous polyps are found in the patient’s gastrointestinal tract.

Anyone who has more than 20 adenomatous polyps in their large intestine should have genetic testing and genetic counseling. Genetic testing uses blood or a cheek swab to obtain DNA that is then tested to determine if there is an APC gene mutation. Once a mutation is identified in an individual, his or her family members can be screened for that mutation. Patients and families with FAP will benefit by joining a hereditary colon cancer registry.

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