Polyp (medicine)

While colon polyps are not commonly associated with symptoms, occasionally they may cause rectal bleeding, and on rare occasions pain, diarrhea or constipation.[9] They are a concern because of the potential for colon cancer being present microscopically, and the risk of benign colon polyps becoming malignant over time.[10] Since most polyps are asymptomatic, they are usually discovered at the time of colon cancer screening. Common screening methods are occult blood test, colonoscopy with a modern flexible endoscope, sigmoidoscopy ( usually with the older rigid endoscope), lower gastrointestinal series (barium enema), digital rectal examination (DRE), virtual colonoscopy or Cologuard.[11] The polyps are routinely removed at the time of colonoscopy, either with a wire loop known as a polypectomy snare (first description by P. Deyhle, Germany, 1970),[12] or with biopsy forceps. If an adenomatous polyp is found, it must be removed, since such a polyp is pre-cancerous and has a propensity to become cancerous. For certainty, all polyps which are found by any diagnostic modality, are removed by a colonoscopy. Although colon cancer is usually not found in polyps smaller than 2.5 cm, all polyps found are removed since their removal reduces the likelihood of future colon cancer. When adenomatous polyps are removed, a repeat colonoscopy is usually performed three to five years later.

Most colon polyps can be categorized as sporadic.

Micrograph of a Peutz–Jeghers colonic polyp - a type of hamartomatous polyp. H&E stain.

• Familial adenomatous polyposis
• Peutz–Jeghers syndrome
• Turcot syndrome
• Juvenile polyposis syndrome
• Cowden disease
• Bannayan–Riley–Ruvalcaba syndrome (Bannayan–Zonana syndrome)
• Gardner's syndrome
• Serrated polyposis syndrome

• Cronkhite–Canada syndrome

• Malignant
• Hamartomatous
• Hyperplastic
• Inflammatory: Inflammatory fibroid polyp

Adenomatous polyps, or adenomas, are polyps that grow on the lining of the colon and which carry a high risk of cancer. The adenomatous polyp is considered pre-malignant, i.e., likely to develop into colon cancer.[13] The other types of polyps that can occur in the colon are hyperplastic and inflammatory polyps, which are unlikely to develop into colorectal cancer.

About 5% of people aged 60 will have at least one adenomatous polyp of 1 cm diameter or greater.[14] Multiple adenomatous polyps often result from familial polyposis coli or familial adenomatous polyposis, a condition that carries a very high risk of colon cancer.

Adenomas constitute approximately 10% of digestive polyps. Most polyps (approximately 90%) are small, usually less than 1 cm in diameter, and have a small potential for malignancy. The remaining 10% of adenomas are larger than 1 cm and approach a 10% chance of containing invasive cancer.[15]

There are three types of adenomatous polyp:

• Tubular adenomas (tube-like shape) are the most common of the adenomatous polyps; they may occur everywhere in the colon and they are the least likely colon polyps to develop into colon cancer
• Tubulovillous
• Villous adenomas are commonly found in the rectal area and they are normally larger in size than the other two types of adenomas. They tend to be non-pedunculated, velvety, or cauliflower-like in appearance and they are associated with the highest morbidity and mortality rates of all polyps. They can cause hypersecretory syndromes characterized by hypokalemia and profuse mucous discharge, and can harbor carcinoma in situ or invasive carcinoma more frequently than other adenomas.

The risks of progression to colorectal cancer increases if the polyp is larger than 1 cm and contains a higher percentage of villous component. Also, the shape of the polyps is related to the risk of progression into carcinoma. Polyps that are pedunculated (with a stalk) are usually less dangerous than sessile polyps (flat polyps). Sessile polyps have a shorter pathway for migration of invasive cells from the tumor into submucosal and more distant structures, and they are also more difficult to remove and to ascertain. Sessile polyps larger than 2 cm usually contain villous features, have a higher malignant potential, and tend to recur following colonoscopic polypectomy.[16]

Although polyps do not carry significant risk of colon cancer, tubular adenomatous polyps may become cancerous when they grow larger. Larger tubular adenomatous polyps have an increased risk of malignancy when larger because then they develop more villous components and may become sessile.

It is estimated that an individual whose parents have been diagnosed with an adenomatous polyp has a 50% greater chance to develop colon cancer than individuals with no family history of colonic polyps.[17] As of 2019 there is no way to establish the risks of colon polyps of patients with a family history of them. Overall, nearly 6% of the population, regardless of family history, is at risk of developing colon cancer.

Screening for colonic polyps as well as preventing them has become an important part of the management of the condition. Medical societies have established guidelines for colorectal screening in order to prevent adenomatous polyps and to minimize the chances of developing colon cancer. It is believed that some changes in the diet might be helpful in preventing polyps from occurring, but there is no other way to prevent the polyps from developing into cancerous growths than detecting and removing them.

Colon polyps as they grow can sometimes cause bleeding within the intestine, which can be detected by an occult blood test. According to American Cancer Society guidelines, people over 50 should have an annual occult blood test. People in their 50s are recommended to have flexible sigmoidoscopies performed once every 3 to 5 years to detect any abnormal growth which could be an adenomatous polyp. If adenomatous polyps are detected during this procedure, a colonoscopy is recommended. Medical societies recommend colonoscopies every ten years starting at age 50 as a necessary screening practice for colon cancer.[11][18] The screening provides an accurate image of the intestine and also allows the removal of the polyp, if found. Once an adenomatous polyp is identified during colonoscopy, there are several methods of removal, including using a snare or a heating device.[19] Colonoscopies are preferred over sigmoidoscopies because they allow the examination of the entire colon and can detect polyps in the upper colon, where more than half of polyps occur.

It has been statistically demonstrated that screening programs are effective in reducing the number of deaths caused by colon cancer due to adenomatous polyps. The risk of complications associated with colonoscopies is approximately 0.35 percent, compared to a lifetime risk of developing colon cancer of around 6 percent.[20] As there is a small likelihood of recurrence, surveillance after polyp removal is recommended.