Neoplastic Polyps

Lecture 17

Polyp• A polyp is a mass that

protrudes into the lumen of the gut.

Tumors of the Small and Large Intestines

Non-neoplastic Polyps 90%Hyperplastic polyps- most commonHamartomatous polypsJuvenile polypsPeutz-Jeghers polypsInflammatory polypsLymphoid polyps

• Neoplastic Polyps:• Benign polyps• Adenomas• Malignant lesions (Polyps)

Adenocarcinoma Squamous cell carcinoma of the anus

Adenomas• A benign epithelial tumor in which the cells

form recognizable glandular structures or in which the cells are derived from glandular epithelium.

Adenomatous Polyps

By definition they are dysplastic and have

malignant potential Time for development of adenomas to cancer is

about 7 to 10 years.

Adenomas

Epidemiology of Adenoma Older age is a major risk factor More common in men Large adenomas (> 9mm) may be more

common in African Americans African Americans have a higher risk of right-

sided colonic adenomas and may present with cancer at a younger age (< 50 years) than

Caucasians.

• There is a well-defined familial predisposition to sporadic adenomas, accounting for about a fourfold greater risk for adenomas among first degree relatives, and also a fourfold greater risk of colorectal carcinoma in any person with adenomas.

Types of adenomas on the basis of the epithelial architecture

• 1. Tubular adenomas• 2. Villous adenomas• 3. Tubulovillous adenomas • 4. Sessile Serrated adenomas

Endoscopic Classification 1. Sessile – base is attached to colon wall usually

large2. Pedunculated – mucosal stalk is interposed

between the polyp and the wall 3. 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 Classification I. Low grade dysplasiaII. High grade dysplasia

Tubular Adenoma The most common -- 80%

Characterized by a complex network of branching

adenomatous glands.

Small and pedunculated.

Morphology of TA

Rectosigmoid -50 %,

Single -50%

• The smallest adenomas are sessile; • Larger adenomas are pedunculated

MicroscopyStalk is covered by normal colonic mucosa

Head is composed of neoplastic epithelium, forming

branching glands lined by tall, hyperchromatic, somewhat disorderly

cell, 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 of villous architecture.

• In the clearly benign lesion, the branching glands are well separated by lamina propria, and the level of dysplasia or cytologic atypia is slight.

• However all degrees of dysplasia may be encountered, ranging up to cancer confined to the mucosa (intramucosal carcinoma) or invasive carcinoma extending into the mucosa of the stalk.

• A frequent finding in any adenoma is superficial erosion of the epithelium,

• the result of mechanical trauma.

Tubular adenoma with a smooth surface and rounded glands. Active inflammation is occasionally present in adenomas, in this case, crypt

dilation and rupture can be seen at the bottom of the field.

Villous adenomas

5-15%Glands- long & straight, creating finger-like projections.

large and sessile.

Morphology of VA

The larger and more ominous. occur in older persons, most commonly in the rectum and rectosigmoid

They generally are sessile, up to 10 cm in diameter, velvety or cauliflower-like masses projecting 1

to 3 cm above the surrounding mucosa.

Microscopy• frondlike villiform extensions of the mucosa

covered by dysplastic, sometimes very disorderly, sometimes piled-up, columnar epithelium.

• Invasive carcinoma is found in as many as 40% of these lesions,

• the frequency being correlated with the size of the polyp.

Villous adenoma with long, slender projections that are reminiscent of small intestinal villi.

Tubulovillous adenomas

26 to 75 % villous component5 to 15 %of adenomas; a broad mix of tubular and villous areas. They are intermediate between the tubular and the

villous lesions in their frequency of having a stalk or being sessile, their size, the degree of dysplasia, and the risk of harboring intramucosal or invasive carcinoma.

Serrated Polyps Display features of both hyperplastic P and adenomaTwo types Sessile serrated adenoma – precursors to large HP in

proximal colon of patients with hyperplastic polyposis

Traditional serrated adenoma – look and behave as conventional adenomas; often pedunculated found more often in distal colon

Sessile serrated adenoma lined by goblet cells without typical cytologic features of dysplasia. This lesion is distinguished from a hyperplastic polyp by extension of the

neoplastic process to the crypts, resulting in lateral growth.

Clinical features of adenomas• The smaller adenomas are usually

asymptomatic, until such time that occult bleeding leads to clinically significant anemia.

• Villous adenomas are much more frequently symptomatic because of overt or occult rectal bleeding.

• The most distal villous adenomas may secrete sufficient amounts of mucosal material rich in protein and potassium to produce hypoproteinemia or hypokalemia.

• On discovery, all adenomas, regardless of their location in the alimentary tract, are to be considered potentially malignant; thus, in practical terms, prompt and adequate excision is mandated.

•98% of all cancers in large

intestine almost always arise in

adenomatous polyps, generally curable by resection

Risk Factors for High grade dysplasia and cancer

Large Size - > 1 cm in diameter are risk factor for containing CRC

Villous histology – adenomatous polyps with > 25percent villous histology are a risk factor for

developing CRC High-grade dysplasia – adenomas with high-grade

dysplasia often coexist with areas of invasive cancer in the polyp.

Number of polyps: three or more is a risk factor

Adenoma with intramucosal carcinoma. A, Cribriform glands interface directly with the lamina propria without an intervening basement membrane.

B, Invasive adenocarcinoma (left) beneath a villous adenoma (right). Note the desmoplastic response to the invasive components.

Plasia