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Genetic and Rare Diseases Information Center (GARD)

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Familial adenomatous polyposis


Other Names for this Disease

  • Adenomatous polyposis coli
  • Adenomatous polyposis of the colon
  • Familial adenomatous polyposis of the colon
  • Familial intestinal polyposis
  • Familial multiple polyposis
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Your Question

I have familial adenomatous polyposis (FAP). Recently, my physicians have identified polyps in the upper portion of my intestine, my gall bladder, and my stomach. Are these all the same type of polyps?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is familial adenomatous polyposis (FAP)?

Familial adenomatous polyposis (FAP) is an inherited colorectal cancer syndrome. Cancer usually develops in the lower part of the digestive system, including the large intestine (colon) and rectum. People with the classic type of familial adenomatous polyposis may begin to develop multiple noncancerous (benign) polyps (growths) in the colon as early as their teenage years. The average age at which an individual develops colon cancer in classic familial adenomatous polyposis is about 39 years. Mutations in the APC gene cause classic familial adenomatous polyposis.[1]

Last updated: 4/6/2010

What types of polyps are associated with familial adenomatous polyposis (FAP)?

Colorectal adenomatous polyps are the most commonly observed polyps in FAP. By age 35, 95% of individuals with FAP have this type of polyp. Adenomatous polyps (often referred to as adenomas) are precancerous growths in which the surface epithelium of the gastrointestinal tract exhibits features of dysplasia. Dysplasia, which describes cellular changes within the lining of the gastrointestinal tract, is graded as mild, moderate, or severe. Severe dysplasia is more likely to have cancer found somewhere within it, and is more likely to progress to cancer.[2] Once they appear, the polyps rapidly increase in number; when colonic expression is fully developed, hundreds to thousands of colonic adenomatous polyps are typically observed. Unless the colon is removed, these polyps will become malignant (cancerous).[1][2]

Gastric (stomach) polyps can be either fundic-gland or adenomatous. Gastric fundic-gland polyps are hamartomatous (characterized by growth of normal-appearing tissue that builds up into a noncancerous tumor which can form into cancer over time). They occur in approximately half of individuals with FAP, and are located in the fundus and body of the stomach. Although gastric fundic-gland polyps are considered to have little malignancy potential, several reports of gastric adenocarcinoma and high-grade dysplasia have been reported. Gastric adenomatous polyps occur in about 10% of individuals with FAP and are usually confined to the gastric antrum. The risk for gastric cancer is small.[2]

Adenomatous polyps of the duodenum (small bowel) are observed in 50-90% of individuals with FAP, and are commonly found in the second and third portions of the duodenum. The lifetime risk of small bowel malignancy is 4-12%; the majority occur in the duodenum. Adenomatous polyps of the periampullary region (including the duodenal papilla and ampulla of Vater) are seen in at least 50% of individuals. Polyps in this area can cause obstruction of the pancreatic duct resulting in pancreatitis, which occurs at increased frequency in FAP. These polyps are often small and require a side-viewing endoscope for visualization. The risk of malignancy of polyps in the periampullary region is higher than that of adenomas in other parts of the duodenum. [2]

Adenomatous polyposis of the gallbladder has been reported in about 10 cases of FAP. These adenomatous gallbladder lesions are typically discovered late, often when the patient is older than 40. The pathogenesis of gallbladder adenomas is still unclear and it is difficult to assess the risk of malignancy.[3]     
Last updated: 4/6/2010

What other features may be present in familial adenomatous polypsis (FAP)?

Other features that are variably present in FAP include extra-intestinal manifestations such as osteomas, dental abnormalities, congenital hypertrophy of the retinal pigment epithelium (CHRPE) (an eye condition that does not affect vision but can be seen by looking at the retina using a special instrument called an ophthalmoscope), benign cutaneous lesions, adrenal masses, and desmoid tumors (fibrous tumors usually occur in the tissue covering the intestines).[2] People who have many of these other growths in addition to colon polyps are sometimes referred to as having Gardner syndrome.[1]

Several extracolonic cancers (small bowel, stomach, pancreas, thyroid, central nervous system, liver, bile ducts, adrenal gland) occur with a higher incidence in individuals with FAP than in the general population as well.[2]
Last updated: 4/6/2010

References
Other Names for this Disease
  • Adenomatous polyposis coli
  • Adenomatous polyposis of the colon
  • Familial adenomatous polyposis of the colon
  • Familial intestinal polyposis
  • Familial multiple polyposis
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.