Colorectal Polyps and Polyposis Syndromes

Study Notes

Colorectal Polyps and Polyposis Syndromes

Polyps are lesions arising from the mucosa of a viscus, protruding into the lumen. Gastrointestinal (GIT) polyps affect the oral cavity, pharynx, esophagus, stomach, small intestine, colon, rectum, and anus. Other polyps include those of the nose and urinary bladder.
GIT polyps may be sessile (flat) or pedunculated (stalked).
Not all polypoid lesions are polyps. Some resemble polyps (e.g., lipomas, GISTs) but arise from the submucosa, not the mucosa.
Polyposis syndromes are inherited diseases. They cause multiple polyps in the gastrointestinal tract, often with extra-intestinal involvement. Examples include familial adenomatous polyposis (FAP), hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome), and Peutz-Jeghers syndrome.
Colorectal polyps are classified as neoplastic, hyperplastic, hamartomatous, or inflammatory. The most common types of neoplastic polyps (adenomas) are tubular, villous, and tubulo-villous.
Adenomas are benign, but can turn cancerous (adenoma-carcinoma sequence). This transition takes 5-15 years.
Malignant potential of adenomas relates to size, degree of dysplasia, presence of a serrated appearance, and histologic pattern. Villous adenomas are more likely to become malignant (35-40%), followed by tubulovillous (20%), and tubular (<5%).
Hyperplastic polyps are usually solitary but can be multiple. They rarely progress to cancer.
Inflammatory polyps result from inflammatory bowel disease (e.g., ulcerative colitis, Crohn's). These polyps are not cancerous. Cancer arising in inflammatory bowel disease typically originates from flat mucosa.
Hamartomatous polyps show disordered growth. Juvenile polyps are a type and usually affect infants.
Common presentations of colorectal polyps are silent, bleeding per rectum and anemia, prolapse from the anus, colicky pain, and rarely intussusception (telescoping of the bowel). Excessive mucus can be seen with big villous polyps, leading to hypokalemia in rare cases.
Investigations include colonoscopy, CT colonography, and barium enema (less frequently used now). Genetic counseling is essential for patients with polyposis syndromes.
Colonoscopy is crucial for diagnosis and biopsy. It can also treat polyps via polypectomy. CT colonography is helpful, but doesn't allow for biopsy.
The management of colorectal polyps depends on type, number, size, and if malignant. Polypectomy (snaring) is common (suitable for limited polyps).
For malignant colorectal polyps, polypectomy may be sufficient if the cancerous polyp is pedunculated and confined to its head; the resection margins are clear, and there are no other unfavorable histological characteristics (such as positive margins, vascular invasion, or poor differentiation).
If the above criteria aren't met, surgical resection is indicated.

Pathological Summary

The colon and rectum are the most common sites, and polyps can be sessile (flat) or pedunculated (stalked).
Virtually all colorectal polyps are neoplastic adenomas. They can be tubular, tubulovillous, or villous.
Intestinal polyps, including colorectal polyps, may arise from sites like the stomach and duodenum; and extra-intestinally, like desmoids and CHRPE.
Colorectal polyps with malignant potential commonly progress into colorectal cancer. Penetrance (probability of developing disease) is 100% in untreated cases of familial adenomatous polyposis (FAP).

Famous Polyposis Syndromes

Familial adenomatous polyposis (FAP)
Lynch syndrome (HNPCC)
Peutz-Jeghers syndrome
Attenuated FAP

Familial Adenomatous Polyposis (FAP)

A rare, inherited disease (autosomal dominant).
Males are affected more often than females.
Affected individuals have a very high chance of developing colorectal cancer if untreated

Screening

Flexible sigmoidoscopic screening is indicated for people with a family history of FAP.
Screening begins at the age of 12 for children of known FAP parents.
Genetic screening is available if a genetic mutation is known.