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Intestinal Polypoid Adenomas

Background

The term intestinal polyp is used to describe any projection arising from a flat mucosa into the intestinal lumen. Polyps can be pedunculated (see first image below) or sessile (see second image below).

Endoscopic view of a pedunculated polyp.

Endoscopic view of a pedunculated polyp.

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Endoscopic view of a sessile polyp.

Endoscopic view of a sessile polyp.

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See Benign or Malignant: Can You Identify These Colonic Lesions?, a Critical Images slideshow, to help identify the features of benign lesions as well as those with malignant potential.

Colonic polyps are usually classified as nonneoplastic, hamartomatous, neoplastic (adenomas and carcinomas), serrated (which can be neoplastic or nonneoplastic), or submucosal (which can be neoplastic or nonneoplastic). Adenomas account for approximately 65% of all colonic polyps, and serrated lesions account for the remaining 35%.
Approximately two thirds of all colorectal carcinomas are believed to arise from adenomas, a finding that underscores the importance of treatment and surveillance of adenomas of the gastrointestinal tract. The focus of this article is adenomatous colonic polyps, as shown in the images below.

Villous adenoma, low-power view. Courtesy of Georg

Villous adenoma, low-power view. Courtesy of George H. Warren, MD.

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High-power view of adenomatous polyp with low-grad

High-power view of adenomatous polyp with low-grade dysplasia. Courtesy of George H. Warren, MD.

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In the United States, colorectal cancer (CRC) is the third most common cause of cancer and the second leading cause of cancer-related death.
Screening for premalignant adenomatous polyps has the potential of preventing CRC. Colorectal adenomatous polyps are therefore targets for intervention and they may also represent biomarkers for CRC risk.

Colonoscopic screening for adenomatous polyps and their removal results in a decreased risk of colon cancer. The National Polyp Study
demonstrated that removal of all colonic adenomas resulted in a 76% to 90% reduction in colon cancer incidence and a 53% reduction in mortality from colon cancer over long-term follow-up compared with historic controls.

A more recent concern is that colonoscopy does not necessarily protect against colon cancers proximal to the splenic flexure (right-sided colon cancers).
This is likely due to a combination of reasons, including technical issues, such as poorer bowel preparation in the right side of the colon and higher rates of missed or incompletely resected polyps in the right side of the colon (that tend to be more flat and more difficult to identify and remove). In addition, it is possible that right-sided polyps have different biologic characteristics that may make them more elusive to detection and more aggressive in their progression.

Despite these potential limitations, physicians should advise patients regarding available options for colorectal polyp and cancer screening. Consensus guidelines on the early detection and surveillance of colorectal cancer and polyps from the United States Preventive Services Task Force (USPSTF)
were most recently published in 2008 and guidelines from the US Multi-Society Task Force (MSTF) on Colorectal Cancer
were updated in 2012.

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