Colon Polyps:
A Possible Precursor to Colon Cancer?

Colon cancer is one of the leading forms of cancer, killing over 50,000 people every year in the United States. While the causes of colon cancer are unknown, one of the major risk factors for colon cancer is a colon polyp.
What Is a Colon Polyp?
A colon polyp is an abnormal growth of tissue on the inner lining of the colon or large intestine. This growth of tissue can be as small as a pea or as large as a golf ball. Polyps can also grow on a stalk or may look like a large, fleshy button growing on the lining of the intestine.

The majority of polyps, especially the small polyps, are not dangerous. Most of these tumors are benign and never develop into cancer. One does need to be wary of larger polyps though. Large polyps may be benign, but may one day develop into cancer.

Causes and Risk Factors for Colon Polyps

The exact cause of colon polyps is unknown, but like many other abnormal tissue growths, certain risk factors are suspected, including:
  • age: Older people are more likely to develop colon polyps. Over ninety percent of cases occur in people over the age of fifty.
  • inflammation: Long-term inflammation of the intestines increases the likelihood of developing colon polyps.
  • family history: If someone in your family has a history of colon cancer or colon polyps, the chances that you'll develop colon polyps are increased.
  • diet: A diet high in fat and low in fiber seems to lead to an increased risk of developing precancerous colon polyps.
  • alcohol and smoking: Excessive drinking and smoking seem to be a risk factor for many different forms of cancer, including colon cancer.
  • a sedentary lifestyle: Waste products tend to stay in the colon longer for people who do not exercise regularly.

What Is Familial Adenomatous Polyposis (FAP)?
Familial adenomatous polyposis or FAP is a hereditary disorder that results in the development of hundreds of polyps in the colon. The disorder is a result of a genetic mutation in the adenomatous polyposis coli gene, which is one of the genes responsible for controlling cell growth. FAP often begins early in a person's life (during the teenage years) and usually does not show any symptoms for many years. If left untreated, it almost always develops into colon cancer.

Symptoms of Colon Polyps

Colon polyps are normally asymptomatic, but some people do experience symptoms, which may include:
  • anal bleeding
  • a change in bowel movements
  • blood in the stool
  • abdominal pain or cramping as a result of a blockage in the colon.

Types of Colon Polyps

Colon polyps can be classified as one of three different types:
  • adenomatous: Adenomatous polyps are the most common type of polyp. Most adenomatous polyps can be found in the rectum and sigmoid colon. The larger this type of polyp grows, the greater the chance that it will be cancerous. Adenomatous polyps can be further subdivided into three different categories: villous, tubular and tubulovillous.
  • hyperplastic: Hyperplastic polyps are normally found in the rectum and descending colon. They are fairly small in size and almost never develop into cancer.
  • inflammatory: Inflammatory polyps usually develop after an inflammation of the colon, such as after a bout of colitis. These polyps may eventually develop into cancer.

Detecting Colon Polyps

Colon polyps are usually detected when screening for colon cancer. Many different screening methods for colon polyps exist, including:
  • medical history examination: The doctor will always inquire first about the patient's personal and family medical history.
  • fecal occult (hidden) blood test: The doctor checks a stool sample for blood.
  • digital rectal exam (DRE): The doctor uses a gloved finger to check the lower part of the rectum for polyps.
  • sigmoidoscopy: A thin tube equipped with a light and video camera is inserted into the rectum to check the rectum and the lower part of the colon for polyps.
  • colonoscopy: Uses a longer tube equipped with a light and video camera to check the rectum and the entire colon for polyps.
  • barium enema: The colon is filled with barium which helps to outline any polyps in the large intestine on an x-ray.

Treatments for Colon Polyps

During an examination or screening for colon cancer, all colon polyps found during a colonoscopy or sigmoidoscopy are removed. This is because the doctor is unable to determine whether the polyp is malignant or benign, so a closer examination is needed.

The polyp is generally removed by a wire loop (snare). The loop is able to simultaneously cut the polyp from the stalk and cauterize the wound to prevent bleeding.

For polyps that are too large for the wire loop or are in places where the snare would be unsafe, surgery may be required.

Preventing Colon Polyps

While you cannot eliminate all risk factors, you can make certain changes to your life to reduce the risk of developing polyps, and colon cancer, including:
  • eating plenty of fruits and vegetables
  • limiting your fat intake
  • getting an adequate amount of calcium and folic acid
  • limiting your alcohol intake
  • quitting smoking
  • exercising daily.
Resources

Jackson Gastroenterology. (updated 2000).Colon polyps and cancer.

Mayo Foundation for Medical Education and Research. (updated 2003). Colon polyps.

National Digestive Diseases Information Clearinghouse. (2003). What I need to know about colon polyps [NIH Publication No. 03-4977].

Penn State: Milton S. Hershey Medical Center. (nd). Colon polyps.

Santoro, M. (updated 2005). Colon polyps.