Polyp• A polyp is a mass thatprotrudes into the lumen ofthe gut.
Tumors of the Small and Large IntestinesNon-neoplastic Polyps 90%Hyperplastic polyps- most commonHamartomatous polypsJuvenile polypsPeutz-Jeghers polypsInflammatory polypsLymphoid polyps
• Neoplastic Polyps:• Benign polyps• Adenomas• Malignant lesions (Polyps)AdenocarcinomaSquamous cell carcinoma of the anus
Adenomas• A benign epithelial tumor in which the cellsform recognizable glandular structures or inwhich the cells are derived from glandularepithelium.
Adenomatous PolypsBy definition they are dysplastic and havemalignant potentialTime for development of adenomas to cancer isabout 7 to 10 years.Adenomas
Epidemiology of AdenomaOlder age is a major risk factorMore common in menLarge adenomas (> 9mm) may be morecommon in African AmericansAfrican Americans have a higher risk of right-sided colonic adenomas and may present withcancer at a younger age (< 50 years) thanCaucasians.
• There is a well-defined familial predispositionto sporadic adenomas, accounting for about afourfold greater risk for adenomas among firstdegree relatives, and also a fourfold greaterrisk of colorectal carcinoma in any person withadenomas.
Types of adenomas on the basis of the epithelial architecture• 1. Tubular adenomas• 2. Villous adenomas• 3. Tubulovillous adenomas• 4. Sessile Serrated adenomas
Endoscopic Classification1. Sessile – base is attached to colon wall usuallylarge2. Pedunculated – mucosal stalk is interposedbetween the polyp and the wall3. Flat – height less than one-half the diameter ofthe lesion.Depressed lesions appear to be particularly likelyto harbor high-grade dysplasia or be malignanteven if small.
Colonic adenomas. A, Pedunculated adenoma .B, Adenoma with a velvety surface. C, Low-magnification photomicrograph of a pedunculated tubular adenoma.
Pathologic ClassificationI. Low grade dysplasiaII. High grade dysplasia
Tubular AdenomaThe most common -- 80%Characterized by a complex network of branchingadenomatous glands.Small andpedunculated.
Morphology of TARectosigmoid -50 %,Single -50%
• The smallest adenomas are sessile;• Larger adenomas are pedunculated
MicroscopyStalk is covered by normal colonic mucosaHead is composed of neoplastic epithelium,formingbranching glandslined by tall, hyperchromatic, somewhat disorderlycell,which may or may not show mucin secretion.
Dysplastic epithelial cells (top) with an increased nuclear-to-cytoplasmic ratio,hyperchromatic and elongated nuclei, and nuclear pseudostratification.
• In some instances there are small foci ofvillous architecture.• In the clearly benign lesion, the branchingglands are well separated by lamina propria,and the level of dysplasia or cytologic atypia isslight.
• However all degrees of dysplasia may beencountered, ranging up to cancer confined tothe mucosa (intramucosal carcinoma) orinvasive carcinoma extending into themucosa of the stalk.
• A frequent finding in any adenoma issuperficial erosion of the epithelium,• the result of mechanical trauma.
Tubular adenoma with a smooth surface and rounded glands. Activeinflammation is occasionally present in adenomas, in this case, cryptdilation and rupture can be seen at the bottom of the field.
Villous adenomas5-15%Glands- long & straight, creating finger-like projections.large and sessile.
Morphology of VAThe larger and more ominous.occur in older persons,most commonly in the rectum and rectosigmoidThey generally are sessile,up to 10 cm in diameter,velvety or cauliflower-like masses projecting 1to 3 cm above the surrounding mucosa.
Microscopy• frondlike villiform extensions of the mucosacovered by dysplastic, sometimes verydisorderly, sometimes piled-up, columnarepithelium.• Invasive carcinoma is found in as many as40% of these lesions,• the frequency being correlated with the sizeof the polyp.
Villous adenoma with long, slender projectionsthat are reminiscent of small intestinal villi.
Tubulovillous adenomas26 to 75 % villous component5 to 15 %of adenomas;a broad mix of tubular and villous areas.They are intermediate between the tubular and thevillous lesions in their frequency of having a stalk orbeing sessile, their size, the degree of dysplasia, andthe risk of harboring intramucosal or invasivecarcinoma.
Serrated PolypsDisplay features of both hyperplastic P and adenomaTwo typesSessile serrated adenoma – precursors to large HP inproximal colon of patients with hyperplasticpolyposisTraditional serrated adenoma – look and behave asconventional adenomas; often pedunculated foundmore often in distal colon
Sessile serrated adenoma lined by goblet cells without typical cytologic features ofdysplasia. This lesion is distinguished from a hyperplastic polyp by extension of theneoplastic process to the crypts, resulting in lateral growth.
Clinical features of adenomas• The smaller adenomas are usuallyasymptomatic, until such time that occultbleeding leads to clinically significant anemia.• Villous adenomas are much more frequentlysymptomatic because of overt or occult rectalbleeding.• The most distal villous adenomas maysecrete sufficient amounts of mucosalmaterial rich in protein and potassium toproduce hypoproteinemia or hypokalemia.
• On discovery, all adenomas, regardless oftheir location in the alimentary tract, are to beconsidered potentially malignant; thus, inpractical terms, prompt and adequateexcision is mandated.
•98%of all cancers in largeintestine almost always arise inadenomatous polyps, generallycurable by resection
Risk Factors for High grade dysplasia and cancerLarge Size - > 1 cm in diameter are risk factor forcontaining CRCVillous histology – adenomatous polyps with > 25percent villous histology are a risk factor fordeveloping CRCHigh-grade dysplasia – adenomas with high-gradedysplasia often coexist with areas of invasive cancerin the polyp.Number of polyps: three or more is a risk factor
Adenoma with intramucosal carcinoma. A, Cribriform glands interface directly withthe lamina propria without an intervening basement membrane.
B, Invasive adenocarcinoma (left) beneath a villous adenoma (right).Note the desmoplastic response to the invasive components.