Serrated polyps of the colon: how reproducible is their classification?

Abstract

For several years, the lack of consensus on definition, nomenclature, natural history, and biology of serrated polyps (SPs) of the colon has created considerable confusion among pathologists. According to the latest WHO classification, the family of SPs comprises hyperplastic polyps (HPs), sessile serrated adenomas/polyps (SSA/Ps), and traditional serrated adenomas (TSAs). The term SSA/P with dysplasia has replaced the category of mixed hyperplastic/adenomatous polyps (MPs). The present study aimed to evaluate the reproducibility of the diagnosis of SPs based on currently available diagnostic criteria and interactive consensus development. In an initial round, H&E slides of 70 cases of SPs were circulated among participating pathologists across Europe. This round was followed by a consensus discussion on diagnostic criteria. A second round was performed on the same 70 cases using the revised criteria and definitions according to the recent WHO classification. Data were evaluated for inter-observer agreement using Kappa statistics. In the initial round, for the total of 70 cases, a fair overall kappa value of 0.318 was reached, while in the second round overall kappa value improved to moderate (kappa = 0.557; p < 0.001). Overall kappa values for each diagnostic category also significantly improved in the final round, reaching 0.977 for HP, 0.912 for SSA/P, and 0.845 for TSA (p < 0.001). The diagnostic reproducibility of SPs improves when strictly defined, standardized diagnostic criteria adopted by consensus are applied.

Endoscopic versus histological characterisation of polyps during screening colonoscopy

“…This led to a position paper by the American Society of Gastrointestinal Endoscopy (ASGE), which set two preconditions for such an approach,12 namely, required accuracy in the prediction of post-polypectomy surveillance intervals of more than 90% and required negative predictive value for adenomatous histology of 90% or more. The recently introduced topic of serrated adenomas and their differential diagnosis in comparison to hyperplastic polyps with still substantial inter-observer variability on histopathological analysis complicates this issue further and does not support a significant role of endoscopic imaging at present because histopathological inter-observer agreement is already rather limited 22. A limitation of our study may therefore be that no uniform histopathology is available.…”

Impact of reassessment of colonic hyperplastic polyps by expert GI pathologists

“…Of the SSA subtypes, concordance was 100 % for SSA and 90 % for pSSA, defined as below the WHO definition threshold for SSA-type crypt number [27]. In contrast, two further studies on interobserver agreement found rather disappointing results [13,14].…”

“…With regards to their relative distribution within the group of serrated lesions, the rise of SSA detection rate over time [10] could be at least partially due to a shift in diagnosis from hyperplastic polyps on histopathological review [11,12]. The distinction between SSA and HP, however, may be difficult, and previous studies have also reported poor to fair interobserver agreement rates for histopathological diagnosis of SSA versus HP, with kappa values ranging from 0.16 to 0.38 [11,13,14]. For these reasons, diagnostic criteria for SSA have been recently refined by several expert panels and consensus conferences [2,15], in the hope of arriving at a more uniform and reproducible histopathological diagnosis.…”

Clinical and endoscopic predictors of cytological dysplasia or cancer in a prospective multicentre study of large sessile serrated adenomas/polyps

“…This has been reported in serrated lesion classification, however all cases were reviewed by subspecialty GI pathologists and with the release of the updated 2010 WHO guidelines recent studies have shown very good reproducibility among pathologists 41. Molecular studies were not performed to document underlying serrated pathway mutations, hence SSA/P-D with conventional adenomatous morphology and without residual SSA/P that were endoscopically and pathologically assessed to be conventional adenomas may have been missed.…”