Grading or Not Grading; Pros and Cons of Grading Dysplasia in Colonic Sessile Serrated Adenoma

Background: Serrated polyps of colon include hyperplastic polyp, sessile serrated adenoma/polyp (SSA/P) and traditional serrated adenoma. SSA/P frequently found in right colon and may show cytological dysplasia either in the form of conventional dysplasia or serrated dysplasia. The dysplasia may be found within the serrated epithelium or adjacent to it. The recent international survey (Amir Samani, et al. College of American Pathologists 2018 Annual Meeting. October 20-24, Chicago, US) shows that about 60% of pathologists use two tier grading system when conventional dysplasia is within the serrated epithelium, and use the term mixed polyp of serrated adenoma and conventional dysplasia when the dysplasia is adjacent to serrated epithelium.Discussion: The dysplasia in SSA/P may resemble conventional dysplasia; however, the molecular changes in those polyps are different from conventional dysplasia and the significance of grading of the conventional dysplasia in SSA/P has not been evaluated. In fact, giving the low grade to dysplastic changes of SSA/P may convey wrong message to clinicians (gastroenterologists and surgeons) that the patient has a low risk lesion and apply the surveillance of adenomas. Of note, the post-polypectomy surveillance guideline in most countries is based on the presence of any dysplasia in SSA/P and not its grading. The fourth edition of WHO classification of tumors of digestive system (2010) discourages the diagnosis of mixed polyp as those polyps are considered to represent dysplastic changes in SSA/P. Post-polypectomy surveillance guideline in most countries has no defined follow up plan for mixed polyp , neither. Conclusion: The current recommendation is to report any dysplastic changes in SSA/P as cytological dysplasia either within the serrated epithelium or adjacent to it. For such lesions, comment on advanced nature of lesion and an educational note such as follows is recommended: SSA/P with dysplasia are advanced lesions with increased propensity to transform to adenocarcinoma. Complete endoscopic removal is recommended. If complete endoscopic removal cannot be achieved, short-term re-endoscopy and biopsy, or surgical resection should be considered.

کلیدواژه ها:

SSA/P ، TSA ، Serrated poylp ، Cytological dysplaisa ، High grade