CHAPTER 34
Polyps of the colon and rectum

Daniel C. Chung¹ and John J. Garber^1,2

¹ Massachusetts General Hospital, Boston, MA, USA

² Translational Medicine at Vertex Pharmaceuticals Boston, MA, USA

The colon is the last part of the intestinal tract, and functions primarily to extract water and solutes from stool. A polyp is any abnormal protrusion of the mucosa into the bowel lumen, and, in contrast to the more proximal intestine, the colon is a common site of benign and malignant polyps.

The detection and treatment of adenomatous polyps through routine screening and early detection are associated with reduced rates of colorectal cancer and mortality. Because a range of polypoid lesions in the large intestine can appear similar to adenomas and adenocarcinomas, it is important to combine endoscopic and histological features to try to distinguish benign from malignant polyps and nonadenomas from adenomas.

Although colonoscopy is the standard approach to identify colon polyps, radiological approaches including CT‐colonography have emerged as an alternative (Figure 34.1). We have also included several variants of adenomas which are likely to be encountered at some point by the endoscopist, including an adenoma associated with a fibrosing desmoplastic response (Figure 34.2), an adenoma displaying the typical features of high‐grade dysplasia (Figure 34.3), which is sometimes used interchangeably with intramucosal carcinoma (Figure 34.4), and an uncommonly encountered malignant polyp (Figure 34.5), which is an adenomatous polyp in which a focus of carcinoma penetrates through the muscularis mucosae. Because the colon is also the site of a large number of benign polyps of diverse etiology, we have also included typical examples of several commonly encountered nonadenomatous polyps, including inflammatory fibroid polyps (Figure 34.6), pseudopolyps, which are most often encountered in the setting of chronic inflammation (Figure 34.7), and hamartomatous polyps (Figure 34.8), which are disorganized tissue growths composed of normal tissue elements. Hamartomatous polyps tend be pedunculated and they are often friable and bleed easily.

Finally, we have included examples of how artificial intelligence and machine learning are being incorporated into colonoscopy to aid with polyp detection (Figure 34.9).

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