Three Pathologic Criteria for Reproducible Diagnosis of Colonic Sessile Serrated Lesion Versus Hyperplastic Polyp

BACKGROUND

Colonic sessile serrated lesions are thought to predispose to ∼30% of colonic adenocarcinomas. This increased risk, compared to benign hyperplastic polyps, makes their distinction vitally important. However, no gold standard exists to differentiate them, and wide observer variability is reported.

METHODS

To better distinguish these polyps, we investigated 94 serrated polyps (53 sessile serrated lesions and 41 hyperplastic polyps), using an easy-to-apply pathologic scoring system that combines, for the first time, three established distinguishing features: polyp morphology, location, and size. As an additional novel approach, polyp size was assessed by serrated biopsy number compared to endoscopic size. RNA expression profiling served as an additional biomarker. The considerable morphologic overlap across serrated polyps was quantitated for the first time. Interobserver variability was assessed by eight expert gastrointestinal pathologists.

RESULTS

By ROC analysis, polyp size by biopsy number performed best, followed by polyp location and morphology (areas under the curves [AUC] 85.9%, 81.2%, 65.9%, respectively). Optimal discrimination combined all three features (AUC 92.9%). For polyp size, biopsy number proved superior to endoscopic size (AUC 85.9% versus 55.2%, p=0.001). Interobserver variability analysis yielded the highest reported Fleiss and Kappa statistics (0.879) and percent agreement (96.8%), showing great promise toward improved diagnosis.

CONCLUSIONS

The proposed three-criteria pathologic system, combining size by biopsy number, location, and morphology, yields an improved, easy to use, and highly reproducible diagnostic approach for differentiating sessile serrated lesions and hyperplastic polyps.

Endoscopic diagnosis of sessile serrated polyp: A systematic review

The aim of the present review was to clarify how we should detect and diagnose sessile serrated polyps (SSP) endoscopically. A systematic search was conducted of MEDLINE from January 2004 through March 2018. Nine findings: (i) proximal location; (ii) size >10 mm; (iii) irregular shape; (iv) indistinctive border; (v) cloud-like surface; (vi) mucus cap; (vii) rim of debris in white-light endoscopy; (viii) dilated vessels; and (ix) dilated crypts (pits) in image-enhanced endoscopy were considered to be candidate discriminators of SSP from hyperplastic polyps. Prospective studies in a general setting are warranted to validate the above-mentioned endoscopic features of SSP during real-time colonoscopy and to determine whether these features are useful for the differential diagnosis of SSP.

Gene expression profiling of serrated polyps identifies annexin A10 as a marker of a sessile serrated adenoma/polyp

Sessile serrated adenomas/polyps (SSA/Ps) are precursors of colon cancer, particularly those that exhibit microsatellite instability. Distinguishing SSA/Ps from the related, but innocuous, microvesicular hyperplastic polyp (MVHP) can be challenging. In this study seven gastrointestinal pathologists reviewed 109 serrated polyps and identified 60 polyps with histological consensus. Microarray analysis was performed on six distal consensus MVHPs < 9 mm, six proximal consensus SSA/Ps > 9 mm, and six normal colon biopsies (three proximal, three distal). Comparative gene expression analysis confirmed the close relationship between SSA/Ps and MVHPs as there was overlapping expression of many genes. However, the gene expression profile in SSA/Ps had stronger and more numerous associations with cancer-related genes compared with MVHPs. Three genes (TFF2, FABP6, and ANXA10) were identified as candidates whose expression can differentiate SSA/Ps from MVHPs, and the differences in expression were confirmed by quantitative RT-PCR. As ANXA10 showed the most promise in differentiating these polyps, the expression of ANXA10 was evaluated by immunohistochemistry in consensus SSA/Ps (n = 26), MVHPs (n = 21), and normal colon (n = 9). Immunohistochemical expression of ANXA10 was not identified in separate samples of normal colon or in the normal colonic epithelium adjacent to the serrated polyps. Consistent with the microarray and quantitative RT-PCR experiments, immunohistochemical expression of ANXA10 was markedly increased in SSA/Ps compared to MVHPs (p < 0.0001). An ANXA10 score ≥ 3 has a sensitivity of 73% and a specificity of 95% in the diagnosis of an SSA/P. In conclusion, we show that SSA/Ps and MVHPs have significant overlap in gene expression, but also important differences, particularly in cancer-related pathways. Expression of ANXA10 may be a potential marker of the serrated pathway to colon cancer.