Colorectal polyps and polyposis syndromes

Abstract

A polyp is defined as any mass protruding into the lumen of a hollow viscus. Colorectal polyps may be classified by their macroscopic appearance as sessile (flat, arising directly from the mucosal layer) or pedunculated (extending from the mucosa through a fibrovascular stalk). Colorectal polyps may also be histologically classified as neoplastic or as non-neoplastic (hyperplastic, hamartomatous, or inflammatory). The neoplastic polyps are of primary importance because they harbor a malignant potential, which represents a stage in the development of colorectal cancer. For this reason, it is essential to identify these polyps at a sufficiently early stage, when a simple outpatient procedure to remove them can interrupt the development of colorectal cancer and prevent disease and death. When invasive carcinoma arises in a polyp, careful consideration must be given to ensuring the adequacy of treatment. Although most neoplastic polyps do not evolve into cancer, it is well accepted that the majority of colorectal carcinomas evolve from adenomatous polyps; the sequence of events leading to this transformation is referred to as the adenoma-to-carcinoma sequence. The presence of a systemic process that promotes the development of multiple gastro-intestinal polyps is termed 'polyposis'. Hereditary gastro-intestinal polyposis syndromes account for approximately 1% of all cases of colorectal cancer and are associated with a broad spectrum of extra-colonic tumors. Early detection and accurate classification of these syndromes are essential, in order to initiate a surveillance program for the early detection of cancer. Several polyposis syndromes have been described, each having its own genetic basis and characteristic polyp distribution, clinical presentation, and malignancy risk. Diagnostic modalities and treatment options for neoplastic polyps-as well as the most prevalent polyposis syndromes-are reviewed below.

Keywords: colonic polyps; polyposis; screening.

Figure 1.

Colonoscopic view of sessile (1a) and pedunculated (1b) polyps.

Figure 2.

Tubular adenoma: low (×400, 2a) and high (×2000, 2b) power magnification views of a hematoxilin–eosin stain. The histological appearance is of branched tubular glands. Courtesy of Mariana Berho, MD.

Figure 3.

Villous adenoma: low (×400, 3a) and high (×2000, 3b) power magnification views of a hematoxilin–eosin stain. The histological appearance is of long finger-like projections. Courtesy of Mariana Berho, MD.

Figure 4.

Colonic mucosa carpeted with adenomatous polyps in a patient with familial adenomatous polyposis.

Figure 5.

Image from a computed tomography of a desmoid tumor in a patient with familial adenomatous polyposis. The tumor is marked by the arrows. The tumor has developed many years after staged total proctocolectomy with end ileostomy. A surgical attempt to resect the tumor was undertaken, without success.