Endoscopic features with associated histological and molecular alterations in serrated polyps with dysplasia: Retrospective analysis of a tertiary case series

Background: Serrated polyps are incompletely understood lesions and include serrated sessile lesion (SSL) without or with dysplasia and traditional serrated adenoma (TSA). Aims: We investigated prevalence and characteristics of serrated lesions, especially SSL with dysplasia (mixed polyps). Methods: This retrospective study analyzed data from consecutive patients referred for colonoscopy at a tertiary care center. Endoscopic and histopathological characteristics of identified lesions were studied. SSLs with dysplasia were molecularly analyzed for mutations and microsatellite instability. Results: Among 1147 patients, a total of 436 polyps were found, including 288 adenomas (66.1 %) and 114 serrated lesions (SLDR 26.2 %). PDR was 34.5 % and ADR was of 30.2 %. Serrated lesions included 75 hyperplastic polyps (17.2 %), 24 SSLs without dysplasia (5.5 %), 6 SSLs with dysplasia (mixed polyps) (1.4 %) and 9 TSA (2.1 %). The mixed polyps were evaluated molecularly: these analyses found no KRAS mutation, a single NRAS mutation in one lesion, the Val600Glu BRAF mutation in four lesions in both their serrated non-dysplastic and dysplastic areas, and microsatellite instability in four lesions, limited to the dysplastic areas. Conclusion: Our single-center experience confirms the high prevalence of serrated lesions, a part of which are SSL with dysplasia. These lesions seem to carry specific molecular alterations.