Understanding the Relationship between
Polyps and Colon Cancer
Steven J. Morris, M.D., FACP,
PCC Board Chair
President, Atlanta Gastroenterology Associates
For patients, and even physicians sometimes, understanding the pathology of a colon polyp often creates concerns and confusion. A primary concern is that some polyps may evolve into colon cancer. Because there are many different types of polyps, however, it sometimes is confusing to determine which polyps do and do not pose a health risk.
Polyp Types
Inflammatory polyps are not true polyps but are a reaction to chronic inflammation of the colon wall and are most often found in patients with ulcerative colitis and Crohn’s disease. Although the underlying disease has a potential for malignant change, the polyps themselves are benign.
Hyperplastic polyps are very common. These are usually small and have no potential to become malignant. The main concern is that they cannot always be distinguished by appearance from the more serious adenomatous polyp so they are frequently removed or biopsied.
Adenomatous polyps are the most common of colon polyps. While this polyp type usually does not develop into cancer for most individuals, they do have malignant potential. In fact, most colon cancers do begin as benign adenomas. Adenomas are traditionally divided into three types as distinguished by their microscopic features: tubular, tubulovillous, and villous.
Polyp Size & Structure
Another critical factor relating to the potential for developing into a cancer, besides the microscopic appearance, is the size of the polyp and the structure. As a general rule the greater the size the more likely the malignant potential. The shape and structure of the polyp may also be important. A pedunculated polyp looks like a mushroom and is easy to remove. Sessile polyps grow directly on the wall and are of greater concern for two reasons. Sessile polyps are more difficult to remove technically and may require more than one procedure. They also may spread more quickly, if they are found to be malignant, into the surrounding tissue.
Polyp Screening & Symptoms
It is important to remember that most colon polyps are asymptomatic and the only way to detect the polyps is by a screening examination. The guidelines for who should be screened and at what ages have been reviewed in a previous issue of this publication and may be found in the winter 2010 edition of the PCC Newsletter. Additional resources are referenced at the end of this article by the CDC, Mayo Clinic, and the American Cancer Society.
If symptoms are present, the most common one is rectal bleeding. This can either be observed by a patient or detected through fecal occult blood tests (FOBT). The incidence of colon polyps increases with age, with both men and women equally affected. In addition, most colon cancers occur after the age of 50. An individual’s genetic predisposition can lower or increase the risk of cancer. Therefore, both patients and their doctors need to be aware of this and act accordingly so that screening begins at the appropriate time. While multiple screening methods currently exist, only colonoscopies provide the chance to both diagnose and remove unwanted polyps during the same procedure. This optimizes the opportunity to remove as many polyps - even the small ones- as possible because they have the potential to become colon cancer. Not every polyp becomes cancer, but almost every colon cancer begins as a small non-cancerous polyp. Since colorectal cancer is the second leading cause of cancer deaths in the United States, accounting for approximately 15% of cancer deaths, it is critical to try and prevent this from occurring. If polyps are removed in a timely fashion, the progression to cancer is eliminated.
The Importance of Follow-Up
One common question patients ask is how often screening colonoscopies should take place. It is critical to note that patients with adenomatous polyps have an increased risk of developing additional polyps. Up to 25% of patients with one polyp may develop additional polyps; therefore the guidelines do recommend more frequent follow-up surveillance in that population. Follow-up may depend on the number of polyps, the exact histology, the patient’s age and family history. Based upon all of these factors and other considerations, patients should consult with their physicians to find out when their next colonoscopy should take place. Although the topic of colon polyps can be confusing, the important thing to remember is that most colorectal cancers do begin with benign polyps. Therefore early screening, detection and removal of these polyps can prevent the development of most colon cancers.
Guideline Resources:
Centers for Disease Control and PreventionMayo Clinic
American Cancer Society Screening Guidelines
For more information on polyps, click here
