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Glossary


Precancerous conditions of the colon and rectum

Precancerous conditions have the potential to develop into cancer. The most common precancerous conditions of the colon and rectum are:

  • adenomatous polyps (adenomas)
  • polyposis syndromes
    • familial adenomatous polyposis (FAP)
    • hereditary non-polyposis colon cancer (HNPCC)

Adenomatous polyps

Adenomatous polyps (adenomas) have the potential to become cancer. It takes an average of 10 years for an adenomatous polyp to develop into an invasive colorectal cancer.

 

The incidence of adenomas increases with age. More than 50% of people 80 years of age or older will have an adenoma. Most will develop in the rectum and sigmoid colon.

 

There are 3 types of adenomatous polyps:

  • tubular adenomas
    • look like a mushroom with a head and a stalk (pedunculated)
    • the outer surface looks like a series of tubes
    • can easily be removed during a colonoscopy
    • are the most common and least likely of all adenomas to contain or develop cancer
    • the larger the tubular adenoma, the greater the chance of it becoming malignant (polyps larger than 2 cm are more likely to develop into cancer)
  • villous adenomas
    • have a fuzzy appearance with numerous long, slender projections
    • are usually flat with a wide, broad base (sessile)
    • can become quite large, making them difficult to remove
    • some of the colon may need to be surgically removed (resected) if the villous adenomas cannot be completely removed by polypectomy
    • are the most likely to develop into cancer, especially if they are large
  • tubulovillous adenomas
    • appear to be a mixture of tubular and villous adenomas
    • the likelihood of them becoming cancerous lies somewhere between the other 2 adenomas

Risk factors

The following risk factors may increase a person's chance of developing adenomatous polyps.

  • increasing age
  • family history of colorectal cancer or polyps
  • personal history of colorectal cancer or polyps

Signs and symptoms

Adenomatous polyps usually do not have any symptoms. They are usually discovered during colorectal screening tests or investigation of other unrelated conditions. The signs and symptoms of adenomatous polyps may include:

  • rectal bleeding
    • if bleeding continues for a long time it may lead to anemia
  • bloody stools
  • diarrhea or constipation
  • decreased amount of stool expelled
  • abdominal pain
  • protrusion (prolapse) of a polyp through the anus
  • bowel obstruction from a large adenoma

Diagnosis

If the signs and symptoms of adenomatous polyps are present, or if the doctor suspects an adenomatous polyp, tests will be done to make a diagnosis. Tests may include:

Treatment

Treatment options for adenomatous polyps may include:

  • removal of the polyp(s) during colonoscopy or sigmoidoscopy
    • Polyps that have a head and a stalk (pedunculated) are easily removed with a flexible wire loop on the endoscope (endoscopic snare polypectomy). The wire is placed around the polyp's stalk, as close to the wall of the colon or rectum as possible, and the wire loop is tightened to cut through the polyp. An electrical current runs through the wire loop to stop the bleeding. The polyp is removed for examination by a pathologist. If cancer cells are found in the area where the stalk of the polyp meets the wall of the colon or rectum, further surgery may be necessary to completely remove the cancer.
  • removal of the part of the colon that has the polyp(s)
    • Sessile polyps cannot be removed as easily as pedunculated polyps because they lie flat against the wall of the colon or rectum. Surgery is usually necessary to completely remove a sessile polyp and to give the pathologist a good sample for diagnosis.

Polyposis syndromes

Some people have an uncommon inherited condition that causes them to develop large numbers of polyps (polyposis syndrome). Polyposis syndromes greatly increases a person's risk of developing colorectal cancer and people with these syndromes are often treated as having a precancerous condition. The 2 main types of polyposis syndromes are:

  • familial adenomatous polyposis (FAP)
    • causes hundreds to thousands of polyps to develop on the lining of the colon and rectum
    • if not treated, almost all people with FAP will develop colorectal cancer
    • accounts for 1% of all colorectal cancers
    • identified through a family history record and genetic testing
  • hereditary non-polyposis colon cancer (HNPCC)
    • polyps are present, but not in as large numbers as in FAP
    • people with this syndrome have an estimated 70–80% lifetime risk of developing colorectal cancer
    • accounts for 3–5% of all colorectal cancers
    • identified through a family history record and genetic testing

Risk factors

Family history of FAP or HNPCC increases a person's chance of developing a polyposis syndrome.

Signs and symptoms

Polyposis syndromes generally do not have any symptoms. Rare symptoms may include:

  • bleeding, especially from polyps in the rectum
  • intestinal blockage or obstruction from a very large polyp

Diagnosis

If the signs and symptoms of polyposis syndromes are present, or if the doctor suspects polyposis syndromes, tests will be done to make a diagnosis. Tests may include:

  • genetic testing
  • sigmoidoscopy
  • colonoscopy

Treatment

Treatment options for polyposis syndromes may include:

Treatment of familial adenomatous polyposis (FAP)

The risk of a person with FAP developing colorectal cancer is almost 100% by the age of 40. The only known way to reduce their risk of colorectal cancer is to remove the colon and part or the entire rectum early in life (between 15 and 20 years of age) or as soon as FAP is diagnosed. Types of surgery include:

  • subtotal colectomy
    • Most of the colon is removed and the small intestine is connected to the remaining part of the rectum.
    • People who have a subtotal colectomy will need to have regular sigmoidoscopies to check for polyps in the remaining part of the rectum.
  • colectomy
    • The colon and part of the rectum are removed and the small intestine is connected to the remaining part of the rectum (rectum-sparing surgery).
    • People who have a colectomy with rectum-sparing surgery will need to have regular sigmoidoscopies to check for polyps in the remaining part of the rectum.
  • proctocolectomy
    • The colon and the entire rectum are removed and the small intestine is connected to an opening in the abdomen (ileostomy) that allows the body to get rid of waste.
    • Some people with FAP may be able to have a restorative proctocolectomy in which the small intestine is connected to the anus.

Treatment of hereditary non-polyposis colon cancer (HNPCC)

People with HNPCC have a 70–80%risk of developing colorectal cancer in their lifetime. Most cases of colorectal cancer occur on the left side of the colon (descending colon). People with HNPCC tend to have colorectal cancer on the right side of the colon (ascending colon). Surgery is the only known way to reduce the risk of colorectal cancer in these people. Types of surgery include:

  • subtotal colectomy
    • Most of the colon is removed and the small intestine is connected to the sigmoid colon or the remaining part of the rectum.
    • People who have a subtotal colectomy will need to have regular sigmoidoscopies to check for polyps in the remaining part of the rectum.
  • colectomy
    • The colon and sometimes part of the rectum are removed and the small intestine is then connected to the remaining part of the rectum (rectum-sparing surgery).
    • People who have a colectomy with rectum-sparing surgery will need to have regular sigmoidoscopies to check for polyps in the remaining part of the rectum.

 

Women with HNPCC are also at higher risk of developing uterine and ovarian cancer and may need to have their uterus and ovaries removed. This possibility should be discussed with their doctor.

 

People with HNPCC are also at higher risk of developing stomach, small intestine, liver, bile duct, pancreatic, kidney and brain cancer. It is important that people with HNPCC discuss their risk of developing these types of cancer with their doctors.

References

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