Does Better Specimen Orientation and a Simplified Grading System Promote More Reliable Histologic Interpretation of Serrated Colon Polyps in the Community Practice Setting? Results of a Nationwide Study

Introduction: Colonoscopic surveillance guidelines for serrated polyps (SPs) are predicated upon the histologic characteristics of the index polyp. However, discrimination between SP subtypes [hyperplastic polyps vs. sessile serrated adenoma/polyps (SSA/P)] is often unreliable. Materials and Methods: We studied the impact of (1) a novel tissue orientation method, performed in the endoscopy laboratory, whereby polyps are flattened in a small paper envelope immediately after resection (modified protocol); and (2) 2012 consensus-modified criteria (CM-2012). These interventions were compared with conventional tissue-handling protocol (CP) and traditional 2008 World Health Organization criteria (WHO). Twenty blinded community pathologists from around the United States scored 100, independent, 0.5 to 2.0 cm, proximal colonic SPs randomly selected from a 2-site tissue section archive. We compared interobserver agreement and diagnostic grading. Results: Interobserver agreement was higher using CM-2012 than WHO criteria (absolute agreement: 13% vs. 4%, P < 0.01; 75% agreement: 54% vs. 38%, P < 0.01). Interobserver agreement was higher with the modified protocol than with CP (WHO absolute agreement: 6% vs. 2%, P > 0.05; WHO 75% agreement: 46% vs. 30%, P > 0.05, and CM-2012 absolute agreement: 20% vs. 6%, P=0.07; CM-2012 75% agreement: 66% vs. 42%, P=0.03). Compared with WHO, use of CM-2012 criteria resulted in fewer diagnoses of "indeterminate"; more diagnoses of SSA/P (P < 0.01); and "upgraded" the diagnosis from hyperplastic polyps to SSA/P in approximately 7% of cases. These observations were independent of polyp size, patient gender, and study site. Conclusions: Simple enhancements to postresection SP handling and diagnostic criteria markedly improve interobserver agreement of SP diagnosis among nongastrointestinal community pathologists. This finding, if confirmed, has important implications for SP colonoscopy surveillance guidelines.