|Classification and external resources|
Polyp of sigmoid colon as revealed by colonoscopy. Approximately 1 cm in diameter. The polyp was removed by snare cautery
|ICD-10||K63.5 & various|
A polyp is an abnormal growth of tissue projecting from a mucous membrane. If it is attached to the surface by a narrow elongated stalk, it is said to be pedunculated. If no stalk is present, it is said to be sessile. Polyps are commonly found in the colon, stomach, nose, sinus(es), urinary bladder and uterus. They may also occur elsewhere in the body where mucous membranes exist like the cervix , vocal folds, and small intestine.
|Polyp||Histologic appearance||Risk of malignancy||Picture||Syndromes|
|Hyperplastic||Serrated unbranched crypts||None||Hyperplastic polyposis syndrome|
|Sessile serrated adenoma||Similar to hyperplastic with hyperserration, dilated/branched crypt base, prominent mucin cells at crypt base||Yes|
|Inflammatory||Raised mucosa/submucosa with inflammation||If dysplasia develops||Inflammatory Bowel Disease, ulcers, infections, mucosal prolapse|
|Tubular Adenoma (Villous, Tubulovillous)||Tubular glands with elongated nuclei (at least low-grade atypia)||Yes|
|Traditional Serrated Adenoma||Serrated crypts, often villous architecture, with cytologic atypia, eosinophilic cells||Yes|
|Peutz-Jeghers Polyp||Smooth muscle bundles between nonneoplastic epithelium, "Christmas tree" appearance||No||Peutz–Jeghers syndrome|
|Juvenile Polyp||Cystically dilated glands with expanded lamina propria||Not inherently, may develop dysplasia||Juvenile polyposis syndrome, identical polyps in Cronkhite-Canada syndrome|
|Hamartomatous Polyp (Cowden Syndrome)||Variable; classical mildly fibrotic polyp with disorganized mucosa and splaying of muscularis mucosae; also inflammatory, juvenile, lipoma, ganglioneuroma, lymphoid||No||Cowden syndrome|
|Inflammatory fibroid polyp||Spindle cells with concentric arrangements of spindle cells around blood vessels and inflammation rich in eosinophils||none|
Colorectal polyp 
Colon polyps are not commonly associated with symptoms. Occasionally rectal bleeding, and on rare occasions pain, diarrhea or constipation may occur because of colon polyps. Colon polyps are a concern because of the potential for colon cancer being present microscopically and the risk of benign colon polyps transforming over time into malignant ones. Since most polyps are asymptomatic, they are usually discovered at the time of colon cancer screening. Common screening methods are digital rectal examination (DRE), sigmoidoscopy (usually flexible sigmoidoscopy, using a flexible endoscope, but more rarely the older rigid sigmoidoscopy, using a rigid endoscope), lower gastrointestinal series (barium enema), colonoscopy, and virtual colonoscopy. The polyps are routinely removed at the time of colonoscopy either with a polypectomy snare (first description by P. Deyhle, Germany, 1970) or with biopsy forceps. If an adenomatous polyp is found with sigmoidoscopy or if a polyp is found with any other diagnostic modality, the patient must undergo colonoscopy for removal of the polyp(s). Even though colon cancer is usually not found in polyps smaller than 2.5 cm, all polyps found are removed since the removal of polyps reduces the future likelihood of developing colon cancer. When adenomatous polyps are removed, a repeat colonoscopy is usually performed in three to five 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
Non-inherited polyposis syndromes 
Types of colon polyps 
Endometrial polyp 
An endometrial polyp or uterine polyp is a polyp or lesion in the lining of the uterus (endometrium) that takes up space within the uterine cavity. Commonly occurring, they are experienced by up to 10% of women. They may have a large flat base (sessile) or be attached to the uterus by an elongated pedicle (pedunculated). Pedunculated polyps are more common than sessile ones. They range in size from a few millimeters to several centimeters. If pedunculated, they can protrude through the cervix into the vagina. Small blood vessels may be present in polyps, particularly large ones.
Cervical 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 the hyperplastic and inflammatory polyps. They 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.
Adenomas constitute approximately 10% of 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 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;
- 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 nonpedunculated, velvety, or cauliflowerlike 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.
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. At this point, there is no method to establish the risks that patients with a family history of colon polyps have to develop these growths. Overall, nearly 6% of the population, regardless of the family history, is at risk to 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 by detecting and removing them.
According to the guidelines established by the American Cancer Society, individuals who reach the age of 40 should perform an occult blood test yearly. Colon polyps as they grow can sometimes cause bleeding within the intestine, which can be detected with the help of this test. Also, persons in their 50s are recommended to have flexible sigmoidoscopies performed once in 3 to 5 years to detect any abnormal growth which could be an adenomatous polyp. If adenomatous polyps are detected during this procedure, it is most likely that the patient will have to undergo a colonoscopy. Medical societies recommend colonscopies every 10 years starting at age 50 as a necessary screening practice for colon cancer. The screening provides an accurate image of the intestine and also allow 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. Colonoscopies are preferred over sigmoidoscopies because they allow the examination of the entire colon, a very important aspect considering that more than half of the colonic polyps occur in the upper colon which is not reached during sigmoidoscopies.
It has been statistically demonstrated that screening programs are effective in reducing the number of deaths caused by colon cancer due to adenomatous polyps. Yet their use is still controversial because of the complications that sometimes arise. However, most of the specialists agree that the benefits of colorectal screening overcome the risks. The risk of complications arising from colonoscopies is half the risk of that of developing colon cancer. As there is a small likelihood of recurrence, surveillance after polyp removal is recommended.
Nasal polyps 
Nasal polyps are polypoidal masses arising mainly from the mucous membranes of the nose and paranasal sinuses. They are overgrowths of the mucosa that frequently accompany allergic rhinitis. They are freely movable and nontender.
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|Wikimedia Commons has media related to: Polyp (medicine)|
- ASGE Website dedicated to colon cancer awareness and early detection.
- ASGE Website educating the public about endoscopy.
- National Institutes of Health polyp website
- Thorough review of polyposis syndromes by Dr. Ali Nawaz Khan with CME available
- Explanation of colon polyps and colon cancer in lay terms.
- "How I Do It" — Removing large or sessile colonic polyps. Dr. Brian Saunders MD FRCP; St. Mark’s Academic Institute; Harrow, Middlesex, UK. Retrieved April 9, 2008.
- FAP Patient Information Sheet