TheriskfordevelopmentofcolonicepithelialdysplasiaandadenocarcinomaisincreasedinpatientswhohavehadcolonicIBDformorethan8to10years.
Polyps are most common in the colon but may occur in the esophagus, stomach, or small intestine. Those without stalks are referred to as sessile. As sessile polyps enlarge, proliferation of cells adjacent to the polyp and the effects of traction on the luminal protrusion may combine to create a stalk. Polyps with stalks are termed pedunculated. In general, intestinal polyps can be classified as nonneoplastic or neoplastic. The most common neoplastic polyp is the adenoma, which has the potential to progress to cancer. Nonneoplastic colonic polyps can be further classified as inflammatory, hamartomatous, or hyperplastic.
The solitary rectal ulcer syndrome is associated with a purely inflammatory polyp. Patients present with the clinical triad of rectal bleeding, mucus discharge, and an inflammatory lesion of the anterior rectal wall. The underlying cause is impaired relaxation of the anorectal sphincter, creating a sharp angle at the anterior rectal shelf. This leads to recurrent abrasion and ulceration of the overlying rectal mucosa. Chronic cycles of injury and healing produce a polypoid mass composed of inflamed and reactive mucosal tissue.
Hamartomatous polyps occur sporadically and as components of various genetically determined or acquired syndromes (
Table 15.6 ). As described previously, hamartomas are disorganized, tumorlike growths composed of mature cell types normally present at the site at which the polyp develops. Hamartomatous polyposis syndromes are rare, but they are important to recognize because of associated intestinal and extraintestinal manifestations and the need to screen family members.
Juvenile polyps are the most common type of hamartomatous polyp. They may be sporadic or syndromic. Sporadic juvenile polyps are usually solitary, but the number varies from 3 to as many as 100 in individuals with the autosomal dominant syndrome of juvenile polyposis. In adults, the sporadic form is sometimes also referred to as an inflammatory polyp, particularly when dense inflammatory infiltrates are present. The vast majority of juvenile polyps occur in children younger than 5 years of age. Juvenile polyps characteristically are located in the rectum and most manifest with rectal bleeding. In some cases, prolapse occurs and the polyp protrudes through the anal sphincter. Dysplasia occurs in a small proportion of (mostly syndromeassociated) juvenile polyps, and the juvenile polyposis syndrome is associated with an increased risk for development of adenocarcinoma within the colon and at other sites (
Table 15.6 ). Colectomy may be required to limit the hemorrhage associated with polyp ulceration in juvenile polyposis.
MORPHOLOGYIndividualsporadicandsyndromicjuvenilepolypsoftenareindistinguishable.Theytypicallyarepedunculated,smooth-surfaced,reddishlesionsthatarelessthan3cmindiameteranddisplaycharacteristiccysticspacesoncutsections.Microscopicexaminationshowsthespacestobedilatedglandsfilledwithmucinandinflammatorydebris(
Fig.15.31A ).Somedatasuggestthatmucosalhyperplasiaistheinitiatingeventinpolypdevelopment,andthismechanismisconsistentwiththediscoverythatmutationsinpathwaysthatregulatecellulargrowth,suchastransforminggrowthfactor-β (TGF-β)signaling,areassociatedwithautosomaldominantjuvenilepolyposis.
Peutz-Jeghers syndrome is a rare autosomal dominant disorder defined by the presence of multiple gastrointestinal hamartomatous polyps and mucocutaneous hyperpigmentation that carries an increased risk for http://ebooksmedicine.net