Colon Polyps
Medical Author:
Michael Santoro, M.D.
Medical Reviewing Author/Editor:
Dennis Lee, M.D.
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.
Next: What other types of polyps are there in addition to adenomas? »
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