Flat Lesions

Abstract

Flat adenomas represent a unique morphological type of polyp and are important precursors of adenocarcinoma of the colon. These polyps can occur sporadically or in patients with hereditary nonpolyposis syndrome (Lynch et al. 1992). Flat adenomas may represent from 8% to one third of all adenomas and early carcinomas in some reports, and are clinically important as these lesions may have a higher proportion of high-grade dysplasia than polypoid adenomas (Wolber 1991; Fujii et al. 1998; Adachi et al. 1988; Rembacken et al. 2000; Saitoh et al. 2001). The majority of research performed in this field has been in Japan and Europe; however, recently these polyps are receiving more attention in Western countries. Flat adenomas can be difficult to detect even with colonoscopy and the use of dye spraying may be necessary to visualize these lesions. This chapter will show the varied appearances of flat lesions in the colon at computed tomography (CT) colonography (CTC).