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Colon Polyps

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Medical Author:

Michael Santoro, MD

Michael Santoro, MD

Dr. Michael Santoro is a Board-certified Internist and Gastroenterologist, who is in clincal practice in Southern California. He did his medical school training at the SUNY-Health and Science Center in Brooklyn. He completed a three-year internal medicine residency at Staton Island University Hospital. This was followed by a three-year fellowship in Gastroenterology and Hepatology at Loma Linda University.

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Medical Editor:

Dennis Lee, MD

Dennis Lee, MD

Dr. Lee was born in Shanghai, China, and received his college and medical training in the United States. He is fluent in English and three Chinese dialects. He graduated with chemistry departmental honors from Harvey Mudd College. He was appointed president of AOA society at UCLA School of Medicine. He underwent internal medicine residency and gastroenterology fellowship training at Cedars Sinai Medical Center.

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What is a colon polyp?

Colon polyps are fleshy growths that occur on the inside (the lining) of the large intestine, also known as the colon. Polyps in the colon are extremely common, and their incidence increases as individuals get older. It is estimated that 50% of the people over the age of 60 will harbor at least one polyp. The significance of polyps is that we know that when certain types of polyps grow large enough, they can become cancerous, and, moreover, colon cancer is the second leading cause of death from cancer in the United Sates. Therefore, screening for colon polyps and removing them before they become cancerous should markedly reduce the incidence of colon cancer.

What types of polyps become cancerous?

The polyps that become cancerous are called adenomatous polyps or adenomas. Adenomas account for approximately 75% of all colon polyps. There are several subtypes of adenoma that differ primarily in the way the cells of the polyp are assembled when they are examined under the microscope. Thus, there are tubular, villous, or tubulo-villous adenomas. Villous adenomas are the most likely to become cancerous, and tubular adenomas are the least likely.

Are there other factors that determine a polyp's chance of becoming cancerous?

Another factor that contributes to a polyp's likelihood of becoming cancerous is its size. The larger a polyp grows, the more likely it is to become cancerous. Once a polyp reaches two centimeters or approximately one inch in size, the risk of cancer is in excess of 20 percent. Therefore, it is advisable to remove polyps of any size, preferably when they are of a small size, to prevent their growth and progression to cancer.