Colonoscopic Features of Sessile Serrated Polyps

Abstract

Sessile serrated polyps (SSPs) are one of the precursors for colon cancer, because of a high BRAF mutation rate. However, the colonoscopic appearances of SSP are still unclear. This study aimed to clarify colonoscopic features of SSPs. Methods: One experienced colonoscopist performed chromocolonoscopy for 190 patients in Australia with the aim to remove all polyps. 166 serrated polyps were detected, of which 54 serrated polyps measuring 5 mm or greater were enrolled. Polyp size was assessed based on resected specimens. One independent colonoscopist reviewed printed photographs of the serrated polyps, blinded to histology. Polyp morphology (flat, protruded), polyp surface (smooth, rough), polyp hue (pale, pink), adherent mucus (thin, thick) and pit pattern (asteroid, elliptic, gyrus-like) were evaluated. Histology was assessed by a single pathologist, and serrated polyps were subclassified as goblet cell (GC) type, microvesicular (MV) type, SSP, traditional serrated adenoma (TSA) and mixed polyp. Results: Ten serrated polyps were excluded because of poor quality photographs, leaving 44 serrated polyps which were studied. The mean size ( ± SD) of the 44 serrated polyps was 8.8 ± 4.0 mm, and 61% were located in the proximal colon. The mean size, location and colonoscopic features of each histological type are shown in the table. All 5 mixed polyps included a TSA component on histology, so these types were combined. The mean size of polyps in the TSA/mixed polyp category was significantly larger than those of MV type and SSP (Bonferroni correction), but there was no significant difference between mean size of MV type and SSP. Except for proximal location, SSPs were very similar in endoscopic appearance to the MV type. Both types of serrated polyps were pale, smooth and flat in appearance with an asteroid pit pattern. The majority of GC type located in the proximal colon showed protruded morphology. The TSA and mixed polyps were distributed evenly and there was no specific morphology. Conclusion: At colonoscopy, GC type can be discriminated from MV type and SSP. However, both MV type and SSP were pale, smooth and flat in appearance with an asteroid pit pattern, making differentiation difficult. The only difference was the anatomical distribution.