Clinicopathological features and endoscopic characteristics of inverted sessile serrated adenomas/polyps

Background and study aims  This study was designed to clarify clinicopathological, endoscopic, and genetic characteristics of inverted sessile serrated adenomas/polyps. Patients and methods  In this retrospective study, we reviewed the pathology reports of patients treated in our hospital between January 2010 and June 2015 and identified sessile serrated adenomas/polyps that were diagnosed with endoscopic resected specimens. Clinicopathological, endoscopic, and genetic features were compared between the inverted and ordinary types. Results  Among the 104 sessile serrated adenomas/polyps, 37 lesions were inverted (35.6 %). The inverted types had two patterns of invasion: expansive and infiltrating growth. Expansive growth was observed in 15 cases (40.5 %) and infiltrating in 22 (59.5 %). Regarding the clinicopathological findings and endoscopic characteristics of the inverted types, presence of adherent mucous, location in the right-side colon, an expanded type-II pit pattern, irregularly dilated vessels, and a depression were demonstrated in 89 % (33/37), 73 % (27/37), 54 % (20/37), 75 % (28/37), and 35 % (13/37), respectively. Contrastingly, these were demonstrated in 86 % (58/67), 84 % (56/67), 55 % (37/67), 58 % (39/67), and 0 % (0/67), respectively, in the ordinary type. In the univariate analysis, male sex and a depression in the adenoma/polyp were significantly associated with inverted types ( P Conclusion  More than 30 % of sessile serrated adenomas/polyps were pathologically diagnosed as inverted, and approximately 40 % of them were of the expansive growth type and easily diagnosed with endoscopy.