Nearly all cases of colorectal cancer begin as a small, non-cancerous polyp. A polyp is an abnormal tissue growth on the inner walls of the colon. Polyps are caused by genetic mutations of the DNA in the cells lining the colon and can be comprised of several different types of tissues and shapes. The identification, removal and prevention of a polyp growth is essential in the fight against colon cancer.
Colon Polyp Types
There are four types of polyp tissues that commonly occur within the colon. Some are benign with essentially no potential to grow into cancer while others are considered pre-cancerous:
Inflammatory Polyps
Inflammatory colon polyps are most often found in patients with ulcerative colitis or Crohn’s disease. They are often called “pseudopolyps” (false polyps), because they are not actually polyps, but rather a reaction to chronic inflammation of the colon wall. While inflammatory polyps will not become colon cancer, they are typically biopsied to verify the type.
Serrated Polyps
Serrated polyps include three related types of polyps: hyperplastic polyps, sessile serrated polyps, and serrated adenomas. Our understanding of serrated polyps has increased significantly over the past decade and is still evolving. The majority of serrated polyps that are identified at colonoscopy are hyperplastic polyps. Hyperplastic polyps are usually very small and found most commonly in the rectum. They are considered to be low risk for cancer. Sessile serrated polyps and serrated adenomas tend to be found in the more proximal (beginning) part of the colon and are associated with a higher risk of progressing to cancer.
Tubular Adenoma (Adenomatous Polyp)
About 70 percent of polyps removed are of the tubular adenoma type. Adenomas carry a definite cancer risk. The risk of cancer becomes greater as the polyp grows larger. If detected early, the polyps can be removed during a colonoscopy before cancer cells have a chance to form. The good news is that tubular adenoma polyps grow slowly and may take years to turn into cancer. Patients with a history of adenomatous polyps must be periodically reexamined. Typically, a repeat colonoscopy is recommended after 3-5 years.
Villous Adenoma (Tubulovillous Adenoma)
About 15 percent of polyps removed are of the villous adenoma type. Villous adenoma is a much more serious polyp that has a very high cancer risk as it grows in size. For larger villous adenomas with a flat sessile shape, surgery may be required to help ensure the polyp(s) is completely removed.
Colon Polyps Shapes
Colon polyps usually occur in one of two shapes: pendunculated and sessile polyps. Polyps can rarely occur in other shapes (e.g. excavated polyp).
Pedunculated Polyps
Polyps that are on stems or stalks are called pendunculated polyps and look similar to mushrooms in shape.
Sessile Polyps
Sessile polyps are flat and broad, without a stalk. Due to their flat nature these polyps can be more difficult to find and remove.
Are Colon Polyps Preventable?
There is no definitive, fail-proof method of preventing colon polyps from forming. Avoiding the risk factors one can control, such as tobacco use or poor diet may help to prevent polyps from forming. When polyps do form, avoiding such risk factors may delay their growth. Chemoprevention (not to be confused with chemotherapy) may be effective in reversing, suppressing or preventing the occurrence of cancer or pre-cancerous polyps. Chemoprevention involves the use of medicines, vitamins or minerals in the diet to prevent or decrease the incidence of disease or factors that can lead to disease.
Patients with a History of Polyps
If you have a history of polyps, getting regular colon screenings is important. Especially for individuals with a history of adenomatous polyps, whose risk of developing additional polyps in the future is about 60 percent. As mentioned above, there are usually no warning symptoms that colon polyps are present. With periodic colonoscopy exams, you can maximize your chances that any new polyp will be detected and removed before cancer cells develop.
Rarely, colon cancer may develop between colonoscopy exams. Fortunately, the cancer is usually small and curable by surgery. A periodic colonoscopy can significantly reduce your risk of colon cancer. Patients that have had adenomatous polyps removed in the past should be especially mindful to follow their colon screening program. Ask your doctor when your next colonoscopy should be performed.
When detected early, more than 90 percent of patients can be cured.
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Studies have shown that the risk of developing polyps can be lowered by supplementation with the following micronutrients and antioxidants:
- calcium
- vitamin D
- folate (folic acid)
- selenium
- vitamin B2
- vitamin B6
- beta-carotene
- *curcurmin (from turmeric)
Low dose aspirin may also protect against the development of polyps. One study demonstrated a 40 percent drop in the incidence of recurrent polyps by taking an 81 mg baby aspirin daily. Interestingly, higher doses were less protective. Fiber, either through diet or supplementation, has not been shown to definitively prevent colon polyps or colon cancer; however, a diet higher in fiber may benefit other gastrointestinal conditions.
