Clinicopathologic Findings of Colorectal Traditional and Sessile Serrated Adenomas in Korea: A Multicenter Study

<i>Background/Aims:</i> Serrated polyps have emerged as important evidence supporting the serrated polyp-neoplasia pathway in colorectal carcinogenesis, an alternate to the classical adenoma-carcinoma sequence. However, there is confusion over the diagnostic criteria for serrated polyps including traditional serrated adenoma (TSA) and sessile serrated adenoma (SSA). In addition, clinical and pathologic characteristics of each are largely unknown and need further exploration. <i>Methods:</i> The 753 polyps that were previously diagnosed as serrated adenoma (SA) from 14 tertiary care university hospitals in Korea between 2003 and 2005 were evaluated for the clinicopathologic findings of TSA and SSA. <i>Results:</i> Among 753 cases, 420 (55.8%) were reclassified as TSA and 56 (7.4%) as SSA. Among the pathologic parameters, crypt branching, crypt dilatation, and horizontal crypts were more frequent in SSA than in TSA (p < 0.001). SSA was larger than TSA (12.6 ± 7.3 vs. 9.8 ± 6.9 mm, p = 0.005), was more likely to be flat type (p = 0.006), and was more frequently located in the proximal colorectum (p = 0.012). There were no significant differences in age, sex, and body mass index between TSA and SSA. <i>Conclusions:</i> Locationand endoscopic features of the polyps with abnormal crypt morphology in histologic findings could be helpful for the diagnosis and classification of SAs.