Polyp (medicine)
A polyp is an abnormal growth of tissue projecting from a mucous membrane. Polyps are commonly found in the colon, stomach, nose, ear, sinus, 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 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:| Polyp | Typical location | Histologic appearance | Risk of malignancy | Picture | Syndromes |
| Hyperplastic polyp | Colorectal | Serrated unbranched crypts | if polyps are more than 100 | Serrated polyposis syndrome | |
| Hyperplastic polyp of the stomach | Stomach | Elongated, tortuous, and cystic foveolae separated by edematous and inflamed stroma. | Gastric hyperplastic polyposis | ||
| Fundic gland polyp | Fundus of stomach | Cystically dilated glands lined by chief cells, parietal cells and mucinous foveolar cells. | Very low or none, when sporadic. | Fundic gland polyposis | |
| Sessile serrated adenoma | Colorectal | Similar to hyperplastic with hyperserration, dilated/branched crypt base, prominent mucin cells at crypt base | Yes | Serrated polyposis syndrome | |
| Inflammatory | Non-specific | Raised mucosa/submucosa with inflammation | If dysplasia develops | Inflammatory bowel disease, ulcers, infections, mucosal prolapse | |
| Tubular Adenoma | Colorectal | Tubular glands with elongated nuclei | Yes | ||
| Traditional serrated adenoma | Colorectal | Serrated crypts, often villous architecture, with cytologic atypia, eosinophilic cells | Yes | Serrated polyposis syndrome | |
| Peutz-Jeghers Polyp | All digestive tract | Smooth muscle bundles between nonneoplastic epithelium, "Christmas tree" appearance | No | Peutz–Jeghers syndrome | |
| Juvenile Polyp | Upper GI tract and colon | Cystically dilated glands with expanded lamina propria | Not inherently, may develop dysplasia | Juvenile polyposis syndrome, identical polyps in Cronkhite–Canada syndrome | |
| Hamartomatous Polyp | Mainly colorectal | 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 | All digestive tract | Spindle cells, featuring concentric arrangements around blood vessels, and inflammation rich in eosinophils | none |
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, lower gastrointestinal series, digital rectal examination, virtual colonoscopy or Cologuard.The polyps are routinely removed at the time of colonoscopy, either with a wire loop known as a polypectomy snare, 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. 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
- 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
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 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
- 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
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.
Screening
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. 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, they can be treated with a polypectomy, minimally invasive surgery or in cases with additional risk factors, a total proctocolectomy. 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. As there is a small likelihood of recurrence, further screening after polyp removal is recommended.