Polyp (medicine)

This article is about the medical condition. For the biological structure, see Polyp.

Polyp (medicine)

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 and small intestine.

Classification

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
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	Yes		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

Colorectal polyp

Main article: 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 with either digital rectal exam (DRE), flexible sigmoidoscopy, Barium enema, colonoscopy or 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 flexible 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

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-Zonana syndrome
• Gardner's syndrome

Non-inherited polyposis syndromes

• Cronkhite-Canada disease
• Eversmeyerous Polypius

Types of colon polyps

• Malignant
• Hamartomatous
• Hyperplastic
• Inflammatory

Endometrial polyp

Main article: 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.

Nasal polyp

Main article: Nasal polyp

Cervical polyp

Main article: Cervical polyp

A cervical polyp is a common benign polyp or tumor on the surface of the cervical canal. They can cause irregular menstrual bleeding or increased pain but often show no symptoms. Treatment consists of simple removal of the polyp and prognosis is generally good. About 1% of cervical polyps will show neoplastic change which may lead to cancer. They are most common in post-menstrual, pre-menopausal women who have given birth.

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, 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 50 per cent of people aged 60 will have at least one adenomatous polyp of 1 cm diameter or greater. Multiple adenomatous polyps often result in familial polyposis coli or familial adenomatous polyposis, a condition that carries a very high risk of colon cancer.

Adenomas comprise 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 polyps:

• 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;
• Tubulovillous
• Villous 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 concerning than sessile polyps (flat). 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% 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. The American Cancer Society has 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. The colon polyps, as they grow might 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. However, colonoscopies are recommended by many physicians as an important part of screening for colon cancer as they provide 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 advised to be performed every 10 years in individuals who reached the age of 50 and who do not suffer from colonic polyps or cancer. 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 proved that the screening programs are effective in reducing the number of deaths caused by colon cancer due to adenomatous polyps. Yet, although these tests are almost 100% safe, their use is still controversial because of the complications that might 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 developing colon cancer. As there is a small likelihood of recurrence, surveillance after polyp removal is recommended.

Causes

Most polyps, with the exception of the inflammatory pseudopolyps, result from some form of genetic mutation in one of the colon lining cells. Fortunately, several, probably at least five, mutations are needed in the same cell before cancer occurs and most benign polyps probably only have one gene mutated. DNA damage occurs surprisingly often.

As colon polyps are common in industrialized countries, it is believed that the lifestyle and dietary choices play an important role in developing any type of colon polyp. Adenomatous polyps are associated with high fat diets, diets that are high in red meat, low fiber diets, smoking and obesity.

Genetics and age are risk factors of developing adenomas. Adenomatous polyps are rare in people younger than 40 years and their incidence increases with age. Yet, the risks of developing adenomas and colon cancer increases if the patient has a family history of polyps or colorectal cancer.

Individuals suffering from genetic disorders such as familial adenomatous polyposis, Hereditary Non-Polyposis Colon Cancer (HNPCC) or Cowden disease have an increased risk of developing adenomas and colorectal cancer.

The family history appears to become an increased risk of developing colon polyps particularly when they are diagnosed before the age of 60. Also, smoking and an unhealthy lifestyle may be accounted as risks of developing colon polyps and colon cancer. Moreover in some studies, higher body mass was positively associated with an increased risk of adenomas leading to colon cancer.

Symptoms

Although most colonic polyps are asymptomatic, the symptoms and their severity depends upon the size of the polyp. Commonly, symptomatic polyps also present with a lower GI bleeding which may range from occult bleeding, as detected by fecal occult testing to frank blood per rectum.

Adenomatous polyps however tend to cause symptoms when they are 2 cm or more in diameter. In these cases, the most common symptom is rectal bleeding. Large polyps may also cause profuse watery diarrhea, which can result in severe potassium deficiency causing muscle weakness.

Symptoms of adenomas include irregular bowel movements including diarrhea or constipation and dark patches of blood in the stool.

Treatment

Some studies have demonstrated that medical treatment with nonsteroidal anti-inflammatory drugs(NSAIDs) decreases the number and the size of colonic polyps. One study suggests that aspirin may be beneficial in reducing the incidence of recurrent colonic polyps, particularly advanced colonic polyps in select patients with a high risk of colon cancer and an acceptably low risk of gastrointestinal bleeding or hemorrhagic stroke. Also, consumption of calcium and folate may confer a modest protective effect, particularly in patients with a history of colonic polyps and low basal consumption levels.

The main treatment for adenomas and other types of colon polyps is colonoscopic polypectomy or colonic resection. Adenomatous polyps may be found during colonoscopies and removed at the same time, depending on their number, type and size. A solitary pedunculated adenoma is usually removed during a colonoscopy and this is generally curative. Yet, when a single adenomatous polyp is found, there is an increased risk that others will also develop.

Although the recurrence rate is small, colonoscopy is recommended as follow-up treatment.

Multiple adenomas, often associated with familial adenomatous polyposis, are treated with colonic resection. Also, large sessile polyps or recurrent polyps are also cured with colonic resection. The procedure may include a total colectomy, subtotal colectomy with rectal sparing, or segmental resection.

External links

• 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.