Serrated colorectal polyps in inflammatory bowel disease

Serrated colorectal polyps, which, besides hyperplastic polyps, comprise sessile serrated adenomas/polyps and traditional serrated adenomas, are presumptive precursors of at least 20% of sporadic colorectal carcinomas; however, their significance in patients with inflammatory bowel disease is unclear. We retrospectively evaluated 78 serrated polyps, removed over a 14-year period from 6602 inflammatory bowel disease patients undergoing endoscopic surveillance, with respect to morphologic, clinicopathologic, and molecular features, and compared rates of advanced neoplasia (high-grade dysplasia and carcinoma) development following the index serrated polyp diagnosis to reference inflammatory bowel disease cohorts without serrated polyps. Serrated polyps negative for dysplasia, which morphologically resembled sporadic sessile serrated adenoma/polyps, occurred mainly in females, in the proximal colon, and contained BRAF mutations. Serrated polyps with low-grade dysplasia resembled sporadic traditional serrated adenomas and occurred mainly in males, in the distal colon, and contained KRAS mutations. Serrated polyps indefinite for dysplasia were morphologically heterogeneous, but similar to serrated polyps positive for low-grade dysplasia with respect to male predominance, left-sided location, and KRAS mutation rates. Rates of prevalent neoplasia associated with serrated polyps positive for low-grade dysplasia, indefinite for dysplasia, and negative for dysplasia were 76, 39, and 11%, respectively (P<0.001). Actuarial 10-year rates of incident advanced neoplasia after an initial diagnosis of serrated polyp positive for low-grade dysplasia, indefinite for dysplasia, and negative for dysplasia were 17, 8, and 0%, respectively, the first and last being significantly different (P=0.02) and comparable to those of corresponding reference populations of inflammatory bowel disease patients with and without low-grade dysplasia at baseline, respectively. We conclude that in serrated polyps from inflammatory bowel disease patients, dysplasia grade correlates with morphology, sex, anatomic location, BRAF and KRAS mutation status, prevalent conventional neoplasia, and rates of advanced neoplasia development.