Types of Colon Polyps

Colon Polyps May or May Not Increase Cancer Risk, Depending on Type

Colon Polyp, Drawing
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There are many types of colon polyps, which can be various shapes and sizes. It helps to learn about the different types of colon polyps so you know whether they increase your risk of colon cancer. You can work with your doctor to develop an appropriate treatment plan if you are diagnosed with colon polyps.

What Are Colon Polyps?

"Polyp" is a general term used to describe a benign (noncancerous) growth on the lining, or inside, of a mucous membrane.

This includes mucous membranes that are found in the digestive tract, including the colon and the nasal passages. Other areas with mucous membranes, such as the mouth, uterus, bladder and the genital areas can develop polyps as well.

The likelihood of having polyps increases with age. Approximately half of people over the age of 60 have at least one polyp and often more.

Polyps are considered precancerous, which means that they are not cancer, but if left untreated, they may develop into cancer. Fortunately, colon polyps typically are found during routine colon cancer screening tests, such as a colonoscopy or flexible sigmoidoscopy. When found, these growths can be removed, which reduces the likelihood of later developing colon cancer.

Shapes of Colon Polyps

In terms of shape, colon polyps come in two basic varieties: pedunculated and sessile. Pedunculated polyps are mushroom-like tissue growths that are attached to the surface of the mucous membrane by a long, thin stalk, or peduncle.

Sessile polyps sit right on the surface of the mucous membrane. They do not have a stalk. Sessile polyps are flat.

Types of Colon Polyps

The four most common types of colon polyps are inflammatory, adenomatous (adenoma), hyperplastic and villous (tubulovillous) adenoma. In addition to these, two less common polyp types include lymphoid, which are considered rare and benign (noncancerous) and juvenile.

Juvenile refers to the type of polyp, not the age at which polyps first develop.

Inflammatory

Inflammatory colon polyps are found most often in people with an inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis. Inflammatory polyps may be referred to as "pseudopolyps," which means false polyps. This is because these are not true polyps, but rather are a reaction to chronic inflammation in the colon. Inflammatory polyps are benign and generally are not at risk of developing into colon cancer.

Adenomatous

Adenomatous polyps, or adenomas, are the most common type of polyp and make up about 70 percent of the polyps found in the colon. Adenomas can develop into colon cancer, but fortunately, this process typically takes many years. This means that with regular colon cancer screening, these polyps can be found and removed before they develop into colon cancer.

More recent research has found that the sessile, or flat, type of polyps may be more common than originally believed and may be harder to detect on screening.

Despite this, colon cancer screening can drastically reduce your colon cancer risk. Don’t make the mistake of assuming that if you are diagnosed with sessile polyps, you shouldn’t bother with follow-up or additional colon cancer screening. Colon cancer screening saves lives, plain and simple.

Hyperplastic

The word "hyperplastic" refers to the activity of the cells making up the polyp. The cells in this type of polyp are increasing in number. Hyperplasia means an abnormal increase in the number of cells in a tissue, with enlargement of the area.

Despite the fact that the cells in hyperplastic polyps are growing and reproducing, these are considered lower risk for developing into cancer. Even so, hyperplastic polyps are removed during colon cancer screening when they are found. This allows your doctor to check the polyp thoroughly and make sure it is not showing signs of cancer.

Villous or Tubulovillous Adenoma

Approximately 15 percent of polyps that are found and removed with colon cancer screening are villous or tubulovillous adenomas. These polyps are more dangerous because they have the highest likelihood of developing into colon cancer. Villous adenomas may be sessile, or flat, making them more difficult to remove. Smaller villous adenoma polyps may be removed during a colonoscopy, while larger polyps of this type may require surgery for complete removal.

Cell Types In Colon Polyps

Finally, polyps also are defined by the type of cells found in them. In general, cells in polyps are considered non-neoplastic or neoplastic. Non-neoplastic polyps are unlikely to develop into colon cancer. Polyps comprised of neoplastic cells, such as adenomas, have a higher likelihood of developing into colon cancer.

Fortunately, colon cancer screening allows your health care provider to detect and remove polyps made up of both non-neoplastic and neoplastic cells. If you’re squeamish about the idea of being screened for colon cancer, take a few moments to learn how to prepare for these tests and how not to dread a colonoscopy.

References:

American Cancer Society. Colorectal Cancer: Early Detection. Accessed July 12, 2009. http://www.cancer.org/docroot/CRI/content/CRI_2_6X_Colorectal_Cancer_Early_Detection_10.asp

Three Rivers Endoscopy Center. What is a Colon Polyp? Accessed July 12, 2009. http://www.gihealth.com/html/education/colonpolyps.html

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