Comparison of sessile serrated adenoma (SSA) histopathologic diagnostic criteria and their effect on reclassification rate of microvesicular hyperplastic polyps to SSA

Background: During the past two decades sessile serrated adenomas (SSA) received considerable attention due to their increased risk of leading to colorectal carcinoma (CRC). CRCs arising from SSA have frequently been associated with interval cancers (those arising after negative colonoscopy). Diagnosis of these lesions can be challenging, as both macroscopic and microscopic features show similarities to microvesicular hyperplastic polyps (MVHP). Since there is almost no malignant potential of MVHP, it is critical to distinguish them from SSA in order to determine the appropriate follow up. Aims: The aims of our study were to compare the major classification criteria available in the literature for the diagnosis of SSAs and to use these criteria to examine the reclassification rate of MVHP to SSA. Methods: Colorectal polyps diagnosed between 2010 and 2014 at the 1st Department of Pathology and Experimental Cancer Research were searched for samples with descriptions matching serrated lesions. For the diagnosis of SSAs the criteria recommended by Rex et al. were used. The remaining serrated lesions were classified using the WHO 2010 criteria. These lesions were then reanalyzed using seven major histopathological classification studies (Aust 2010, Chung 2008, Higuchi 2005, Mohammadi 2011, Rex 2012, WHO 2010, Yao 2011) and reassessed whether they met the diagnostic criteria for the diagnosis of SSA Results: A total of 347 serrated colonic polyps were found that included 50 (14.4%) SSAs, 143 (41.2%) MVHPs, 148 (42.7%) goblet cell rich hyperplastic polyps (GCHP) and 6 (1.7%) traditional serrated adenomas (TSAs). A significant difference for SSA diagnosis was noted between the classification studies, with results varying from 100% (Rex 2012) to 20% (Chung 2008). This difference was also observed in the reclassification rate of MVHP to SSA: ranging from 15 (10.5%) (Rex 2012) to 2 (1.4%) (Chung 2008) of all MVHPs. Conclusions: In conclusion, we would like to emphasize the significant difference among studies differentiating colorectal serrated lesions. It seems to be clear that a universal diagnostic criteria based on prospective clinicopathological studies is needed to avoid the underdiagnosis that can result in inadequate surveillance and increased risk of CRC. This study was supported by the Hungarian Scientific Research Fund (OTKA-K111743 grant).