Evaluation of magnifying colonoscopy in the diagnosis of serrated polyps

Abstract

Aim: To elucidate the colonoscopic features of serrated lesions of the colorectum using magnifying colonoscopy.

Methods: Broad division of serrated lesions of the colorectum into hyperplastic polyps (HPs), traditional serrated adenomas (TSAs), and sessile serrated adenomas/polyps (SSA/Ps) has been proposed on the basis of recent molecular biological studies. However, few reports have examined the colonoscopic features of these divisions, including magnified colonoscopic findings. This study examined 118 lesions excised in our hospital as suspected serrated lesions after magnified observation between January 2008 and September 2011. Patient characteristics (sex, age), conventional colonoscopic findings (location, size, morphology, color, mucin) and magnified colonoscopic findings (pit pattern diagnosis) were interpreted by five colonoscopists with experience in over 1000 colonoscopies, and were compared with histopathological diagnoses. The pit patterns were categorized according to Kudo's classification, but a more detailed investigation was also performed using the subclassification [type II-Open (type II-O), type II-Long (type II-L), or type IV-Serrated (type IV-S)] proposed by Kimura T and Yamano H.

Results: Lesions comprised 23 HPs (23/118: 19.5%), 39 TSAs (39/118: 33.1%: with cancer in one case), 50 SSA/Ps (50/118: 42.4%: complicated with cancer in three cases), and six others (6/118: 5.1%). We excluded six others, including three regular adenomas, one hamartoma, one inflammatory polyp, and one juvenile polyp for further analysis. Conventional colonoscopy showed that SSA/Ps were characterized as larger in diameter than TSAs and HPs (SSA/P vs HP, 13.62 ± 8.62 mm vs 7.74 ± 3.24 mm, P < 0.001; SSA/Ps vs TSA, 13.62 ± 8.62 mm vs 9.89 ± 5.73 mm, P < 0.01); common in the right side of the colon [HPs, 30.4% (7/23): TSAs, 20.5% (8/39): SSA/P, 84.0% (42/50), P < 0.001]; flat-elevated lesion [HPs, 30.4% (7/23): TSAs, 5.1% (2/39): SSA/Ps, 90.0% (45/50), P < 0.001]; normal-colored or pale imucosa [HPs, 34.8% (8/23): TSAs, 10.3% (4/39): SSA/Ps, 80% (40/50), P < 0.001]; and with large amounts of mucin [HPs, 21.7% (5/23): TSAs, 17.9% (7/39): SSA/Ps, 72.0% (36/50), P < 0.001]. In magnified colonoscopic findings, 17 lesions showed either type II pit pattern alone or partial type II pit pattern as the basic architecture, with 14 HPs (14/17, 70.0%) and 3 SSA/Ps. Magnified colonoscopy showed the type II-O pit pattern as characteristic of SSA/Ps [sensitivity 83.7% (41/49), specificity 85.7% (54/63)]. Cancer was also present in three lesions, in all of which a type VI pit pattern was also present within the same lesion. There were four HPs and four TSAs each. The type IV-S pit pattern was characteristic of TSAs [sensitivity 96.7% (30/31), specificity 89.9% (72/81)]. Cancer was present in one lesion, in which a type VI pit pattern was also present within the same lesion. In our study, serrated lesions of the colorectum also possessed the features described in previous reports of conventional colonoscopic findings. The pit pattern diagnosis using magnifying colonoscopy, particularly magnified colonoscopic findings using subclassifications of surface architecture, reflected the pathological characteristics of SSA/Ps and TSAs, and will be useful for colonoscopic diagnosis.

Conclusion: We suggest that this system could be a good diagnostic tool for SSA/Ps using magnifying colonoscopy.

Keywords: Conventional colonoscopy; Hyperplastic polyps; Magnifying colonoscopy; Pit patterns; Serrated adenoma; Serrated lesions; Sessile serrated adenoma/polyp; Traditional serrated adenomas.

Figure 1

Type II pit patterns and subclassification of surface architectures of serrated lesions of the colon and rectum. A: Conventional type II pit pattern. Regular array of star-shaped, uniform pits with serrated architecture; B: Type II-Open pit pattern. Star-shaped pits similar to conventional type II pits, but with dilated openings of the glandular crypts; C: Type II-Long pit pattern. Similar to type II pits, but elongated without dilation; D: Type IV-Serrated pit pattern. Also called “pine cone-shaped.” Villiform with a serrated architecture; E-I: Mixture of example pit patterns (E: Type II with IV-S; F: Type II-L with IV-S; G: Type II-O with II-L; H: Type II-O with IV-S; I: Type IV-S with II-L).

Figure 2

Classification of 118 subject lesions. Ratio of each lesions [traditional serrated adenomas (TSAs), and sessile serrated adenomas/polyps (SSA/Ps) and others].

Figure 3

Adenocarcinoma (tub1) in sessile serrated adenomas/polyps case. A 60-year-old woman had a tumor lesion in the cecum, which was flat and elevated, that is a so-called lateral spreading tumor (LST), 45 mm in diameter. A, B: Standard view. A 45-mm LST lesion with large amounts of mucin is evident in the cecum. The flat portion is somewhat discolored compared with the surrounding mucosa. The protruded portion on the anal side is reddish in the center; C: Indigo carmine staining. The center of the protruded portion on the anal side is flat; D: Indigo carmine staining, enlarged image (yellow square in 3C). Type II-Long pit pattern is evident; E: Indigo carmine staining, enlarged image (blue square in 3C). Type II-Open pit pattern is evident; F: Indigo carmine staining, enlarged image (black square in 3C). We diagnosed as type VI pit pattern, because high density of crypts and irregular pit pattern were evident; G: Comparison of stereomicroscopic and colonoscopic images; H: Enlarged image of flat portion. Although basically type II, dilated duct openings are evident; I: Enlarged image of protruded portion on the anal side. An irregular surface architecture is evident; J: HE magnifying glass image (yellow line in Figure 3G). We examined HE staining (Figure 3J-L) using the yellow cutting line of endoscopically resected tissue (yellow arrow side tissue); K: Central part of the protrusion on the anal side (blue square in Figure 3J). Highly differentiated ductal cancer corresponding to type VI pits is evident; L: Dilatation of crypts and deformation in the horizontal direction at the bottom of the crypts are evident in the flat portion (red square in Figure 3J). Sessile serrated adenomas/polyps was diagnosed.