Predictive Chromoendoscopy of Serrated Polyps: Is the Pendulum Swinging Toward the Pit Pattern?

Endoscopic polypectomy is currently one of the most effective interventions for the prevention of colorectal cancer (CRC). Although the most common carcinoma precursor is the tubular adenoma, the detection, diagnosis, and follow-up of serrated precursors are also of clinical importance since the serrated pathway is implicated in about 30% of CRC [1, 2]. Serrated polyps can be categorized into three groups: the frequently encountered hyperplastic polyps (HPs) which are flat and distal; sessile serrated adenomas/polyps (SSA/Ps) which are flat, proximal, and account for about 10% of all serrated polyps; and traditional serrated adenomas (TSAs) which are distal, protruding, and account for a small percentage of serrated polyps [3]. HPs are further divided into microvesicular (MVHP) and goblet cell-rich (GCHP) types and are believed to be the precursors of SSA/Ps and TSAs, respectively. Although by definition SSA/Ps are non-dysplastic, they acquire cytologic dysplasia as they progress to CRC. Conversely, all TSAs harbor cytologic dysplasia. Thus, both SSA/P and TSA are established precursors of CRC. Detection and diagnosis of TSAs are straightforward given their unique endoscopic and histologic features. In contrast, HPs and SSA/Ps have similar endoscopic appearances and overlapping histologic features, complicating endoscopic and pathologic differentiation between the two lesions [4, 5]. Furthermore, based on recent data, distinguishing SSA/Ps from HPs may also have some significance for metachronous risk assessment [6], and therefore, differentiating HPs from SSA/Ps is a common concern for endoscopists. A simple, accurate, and reproducible way to endoscopically distinguish HPs from SSA/Ps would aid endoscopists in their efforts to identify and remove all serrated lesions with malignant potential. Furthermore, these methods would be helpful in implementation of new paradigms in which diminutive polyps are optically diagnosed and either not removed or resected and not recovered for subsequent pathologic examination [7]. The American Society for Gastrointestinal Endoscopy (ASGE) Technology Committee’s “Preservation and Incorporation of Valuable endoscopic Innovations” (PIVI) paper provides recommendations for adoption of new technologies or strategies into clinical practice, which can be used to optically diagnose diminutive (≤ 5 mm) polyps [8]. Although developed for adenomas, strategies for optical diagnosis can also be applied by endoscopists for serrated polyps. For example, use of the “diagnose and leave” strategy for serrated polyps could decrease the risk and cost of colonoscopy by obviating the need for polypectomy in polyps that were endoscopically diagnosed as HPs [9]. Alternatively, the “resect and discard” could decrease cost by eliminating the need for pathologic interpretation of serrated polyps that endoscopists were confident were HPs and not SSA/Ps. In this month’s issue of Digestive Diseases and Sciences [10], Aoki et al. in Sapporo, Japan, characterized serrated polyps, conventional adenomas, and CRC using endoscopic, pathologic, and molecular features. In addition to size and location, trained endoscopists used the Paris classification [11] to characterize the shape of the lesions. Magnification chromoendoscopy that has gained popularity in the Far East enables visualization of the “pit pattern” which reflects the colonic pit structure and enables the differentiation of the many types of polyps. The pit patterns are currently categorized by the Kudo classification [12, 13] where Type I indicates normal mucosa, Type II is consistent with HP, and Types III, IV, and V are consistent with dysplastic changes. Disclaimer The contents of this work do not represent the views of the Department of Veterans Affairs or the United States Government.