Polyps are lumps (tumors) that protrude from the lining of the colon. They can be categorized into adenomas or hyperplastic polyps. Hyperplastic polyps are generally not associated with colon cancer, and are not causes of concern. The concerning type of polyps are adenomas, which are benign tumors that can become malignant with time and hence become colon cancer.

The risk of adenomas depends on the microscopic histology and the size of the polyp. Polyps that are smaller than 1 centimeter have a 1 percent chance of having cancerous cells, while polyps that are 2 cm or larger have a 30-50 percent chance of having cancerous cells. Colonic adenomas are extremely common, and in those aged 40 years and over who underwent health screenings at the Samsung Medical Center of Seoul, more than 20 percent were found to have colonic polyps, approximately half of which were adenomas. 

People with colonic polyps generally do not have any symptoms. However, some may develop rectal bleeding, diarrhea, constipation and lower abdominal pain. Those with large polyps can experience an obstruction in the colon.

Methods to identify colonic polyps include sigmoidoscopy, contrast X-ray of the colon, and colonoscopy. If polyps are identified, biopsies will be performed to determine whether the polyps are adenomas or hyperplastic. Adenomas should be removed before they progress to become cancerous.

Colonoscopy

A colonoscopy is a method of examining the colon and the sigmoid colon with an endoscope, where colon cancer and polyps occur most commonly. It is generally not painful and it can identify polyps that are smaller than 0.5 centimeter.

The treatment is different for each type of polyp. Hyperplastic polyps do not progress to cancer so do not need further examination or treatment. However, adenomas, which are precancerous, need a colonoscopy to see the whole colon. This is because approximately 1 in 3 people with adenomas in a sigmoidoscopy have polyps further up in the colon. Not everyone will feel severe pain during a colonoscopy. Recently, colonoscopies are being performed with conscious sedation, and many patients say that it was more difficult to drink the laxative before the procedure than undergoing the procedure itself. The procedure may be difficult to perform if the colon is extremely tortuous and long.

Endoscopic removal

If the biopsy results confirm adenomas, the polyps will need to be removed as they can become cancerous. Before the development of endoscopic methods, the polyps were removed by resecting the colon. Nowadays, the polyps can be removed through endoscopic procedure. Endoscopic removal of polyps is associated with complications in 1 percent of cases, such as bleeding or perforation, which means that the patient will then need to undergo open surgery. Note that there is still a possibility of developing more polyps even after endoscopic removal of the polyps, so you will need regular follow-ups.

The polyps that are removed endoscopically will be examined as a biopsy. This is because simple adenomas that are removed can later be checked to see if they are cancerous when a biopsy is done.

If the cancer is localized to the outer surface (mucosal layer), no additional surgeries are required. But if it has invaded deeper into the tissue (submucosal layer), operations need to be performed. There may not be any cancerous cells after the operation, but if you are fit enough to undergo surgery, it is recommended that you receive it. 

By Rhee Poong-lyul

The author is a doctor at the Division of Gastroenterology at Samsung Medical Center and a professor of Sungkyunkwan University School of Medicine. ― Ed.