Serrated and non-serrated polyps of the colorectum: their prevalence in an unselected case series and correlation of BRAF mutation analysis with the diagnosis of sessile serrated adenoma

Abstract

<h3>Aims</h3> To determine the prevalence of colorectal polyps of different types in an unselected population, and to correlate the diagnosis of dysplastic serrated polyps and sessile serrated adenomas with <i>BRAF</i> mutation analysis. <h3>Methods</h3> Cases of colorectal polyps diagnosed at endoscopy were retrieved from the files of Southern.IML Pathology. All slides were reviewed and the lesions classified histologically. A diagnosis of sessile serrated adenoma was made even if the characteristic features were present focally. If there was more than one polyp of a particular type in any patient, one lesion was chosen at random so that the results represented the number of patients with each type of polyp rather than the total number of polyps. A proportion of the polyps were subjected to <i>BRAF</i> mutation analysis. <h3>Results</h3> We identified 1478 patients. Non-serrated (‘conventional') adenomas were found in 65% of patients, hyperplastic polyps in 30%, sessile serrated adenomas in 3.9%, traditional serrated adenomas in 0.7% and mixed hyperplastic adenomatous polyps in 0.7%. <i>BRAF</i> mutations were found in 90% of lesions diagnosed as sessile serrated adenoma, 29% of hyperplastic polyps of microvesicular type, 36% of traditional serrated adenomas, 100% of mixed hyperplastic adenomatous polyps, and 5% of ‘conventional' adenomas. <h3>Conclusions</h3> Sessile serrated adenomas are encountered commonly in routine endoscopy practice. The histological diagnosis correlates strongly with the presence of <i>BRAF</i> mutation.