Endoscopic discrimination of sessile serrated adenomas from other serrated lesions

Abstract

Abstract. Sessile serrated adenoma (SSA) is a proposed precursor of colorectal carcinogenesis. This study aimed to analyze the potential of endoscopy to discriminate SSA from other serrated lesions, specifically traditional serrated adenoma (TSA) and hyperplastic polyp (HP). Of 145 serrated lesions, 111 sessile serrated lesions including 32 TSAs, 25 SSAs and 54 HPs were analyzed for size, color, location and morphologic features using conventional endoscopy and magnifying chromoendoscopy. SSA was preferentially located in the right colon, whereas TSA and HP were located in the left colon. The sizes of SSA and TSA were larger than those of HP. The lesion color was indistinguishable among TSA, SSA and HP. Macroscopically, a pinecone-like or twotier raised appearance were found more frequently in TSA than in SAA and HP. Under magnified chromoendoscopic observation, the stellar III L pit pattern and fern-like appearance were observed more frequently in TSA than in SAA and HP. In conclusion, endoscopic discrimination between SSA and other sessile serrated lesions based on morphological features was difficult. However, size and location of the lesions facilitated diagnosis. IntroductionSerrated polyps of the colorectum have been the focus of critical reappraisal and intense study in recent years. Previously, the majority of serrated, non-adenomatous polyps were diagnosed as hyperplastic polyps (HPs) and treated as innocuous, benign lesions (1). Subsequently, HP was implicated in the development of colorectal cancer through a putative HP-serrated adenoma-colorectal cancer sequence. At present, the serrated polyps are regarded as heterogeneous lesions with several histological subtypes, including HP, traditional serrated adenoma (TSA) and sessile serrated adenoma (SSA) (2,3).Mounting evidence shows that SSA may be the precursor lesion through the previously described 'serrated pathway' of colorectal carcinogenesis (4), and some investigators recommend that SSA should be clinically managed in a similar manner to conventional adenomas (5). A greater frequency of microsatellite instability has been shown in SSA versus HP or TSA (6). SSA shows a higher frequency of CpG island methylation than conventional HP (7), while showing a higher frequency of BRAF gene mutations and a lower frequency of K-ras gene mutations versus conventional adenoma (8,9). Thus, reliable identification of SSA and its differentiation from other serrated lesions, such as HP and TSA, has important clinical implications and may condition therapeutic attitudes and endoscopic follow-up.Colonoscopy is the only technique currently available that offers the potential to detect and remove colorectal lesions throughout the large intestine. Some authors previously reported the endoscopic features of TSA and HP (10-13). However, the endoscopic features of SSA have yet to be established. This study aimed to compare the endoscopic features of the three sessile serrated lesions, TSA, SSA and HP, and to determine whether SSA can be distinguished from other serrated ...

Serrated polyps of the large intestine: current understanding of diagnosis, pathogenesis, and clinical management

“…SSAs, which are typically larger than HPs and located in the proximal colon, are flat or non-polypoid in morphology [62], often with the appearance of redundant or thickened mucosa altering the contour of a fold, or appearing to be draped over a fold (Fig. 3) [63, 64]. A distinctive feature of SSAs is the mucus cap, comprising a layer of mucus adherent to the surface of the lesion, giving the lesion a yellow or rust-colored appearance in contrast to the surrounding mucosa [65].…”

“…These characteristics were confirmed in a recent prospective study of 158 SSAs in which dominant features included a mucus cap, a rim of bubbles or debris, alteration of the contour of a fold, and loss of the normal mucosal vascular pattern (Table 3). TSA are typically located distally, are more bulky, and tend to be pedunculated or sessile [64].

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“…Recent studies using optical magnification colonoscopy (which is not widely available in Western countries) have attempted to define endoscopic characteristics of SSAs, to allow real-time differentiation [64, 69, 70]. Kimura et al [69] found that a modification to the Kudo pit-pattern classification, a novel type II-O (open) pit-pattern was specific, but not sensitive for SSAs.…”

“…However, Hasegawa et al. [64] found discrimination difficult and instead relied on size and location of lesions. Furthermore, areas of dysplasia within an SSA may theoretically be distinguishable at colonoscopy, particularly with image enhancement techniques and/or optical magnification (Fig.…”

Molecular features of colorectal polyps presenting Kudo’s type II mucosal crypt pattern: are they based on the same mechanism of tumorigenesis?

“…Because of improvements in endoscopic imaging, details of the colorectal mucosa surface can be observed with colonoscopies. However, several studies 11 12 have reported a low diagnostic accuracy of any of the novel endoscopic imaging techniques for differentiating SSAs from HPs. However, Kimura et al 13 have proposed a type II open-shape pit pattern (Type II-O) which was specific to SSA/Ps.…”