A polyp is an abnormal growth of tissue projecting from a mucous membrane. Polyps are commonly found in the colon, stomach, nose, ear, sinus(es), urinary bladder, and uterus. They may also occur elsewhere in the body where there are mucous membranes, including the cervix, vocal folds, and small intestine. If it is attached by a narrow elongated stalk, it is said to be pedunculated; if it is attached without a stalk, it is said to be sessile. Some polyps are tumors (neoplasms) and others are non-neoplastic, for example hyperplastic or dysplastic, which are benign. The neoplastic ones are usually benign, although some can be pre-malignant, or concurrent with a malignancy.
Digestive polyps Relative incidences by location:
Colorectal polyp
While colon polyps are not commonly associated with symptoms, occasionally they may cause rectal bleeding, and on rare occasions pain, diarrhea or constipation. 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. 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. 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), 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. In the US, if a colonoscopy finds polyps that are 10mm or bigger, numerous or abnormal, a repeat colonoscopy may be required (within three years). If one or two are found that are less than 5mm in diameter you may not have to return for a colonoscopy for five or more years. If none are found, a repeat colonoscopy may not be required for 10 years. Most colon polyps can be categorized as sporadic.
Inherited polyposis syndromes
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
Non-inherited polyposis syndromes Cronkhite–Canada syndrome
Types of colon polyps Malignant Hamartomatous Hyperplastic Inflammatory: Inflammatory fibroid polyp
Adenomatous polyps
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. 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. Multiple adenomatous polyps often result from familial polyposis coli or familial adenomatous polyposis, a condition that carries a very high risk of colon cancer.
Types 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. 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.
Risks The risks of progression to colorectal cancer increase 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 ascertain. Sessile polyps larger than 2 cm usually contain villous features, have a higher malignant potential, and tend to recur following colonoscopic polypectomy. 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. Research suggests approximately 5 percent of colon cancer cases are due to an inherited genetic mutation.
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