Serrated polyps of the colon: how reproducible is their classification?

Prevalence, risk factors, and BRAF mutation of colorectal sessile serrated lesions among Vietnamese patients

BACKGROUND

Sessile serrated lesions (SSLs) are considered precancerous colorectal lesions that should be detected and removed to prevent colorectal cancer. Previous studies in Vietnam mainly investigated the adenoma pathway, with limited data on the serrated pathway.

AIM

To evaluate the prevalence, risk factors, and BRAF mutations of SSLs in the Vietnamese population.

METHODS

This is a cross-sectional study conducted on patients with lower gastrointestinal symptoms who underwent colonoscopy at a tertiary hospital in Vietnam. SSLs were diagnosed on histopathology according to the 2019 World Health Organization classification. BRAF mutation analysis was performed using the Sanger DNA sequencing method. The multivariate logistic regression model was used to determine SSL-associated factors.

RESULTS

There were 2489 patients, with a mean age of 52.1 ± 13.1 and a female-to-male ratio of 1:1.1. The prevalence of SSLs was 4.2% [95% confidence interval (CI): 3.5-5.1]. In the multivariate analysis, factors significantly associated with SSLs were age ≥ 40 [odds ratio (OR): 3.303; 95%CI: 1.607-6.790], male sex (OR: 2.032; 95%CI: 1.204-3.429), diabetes mellitus (OR: 2.721; 95%CI: 1.551-4.772), and hypertension (OR: 1.650, 95%CI: 1.045-2.605). The rate of BRAF mutations in SSLs was 35.5%.

CONCLUSION

The prevalence of SSLs was 4.2%. BRAF mutations were present in one-third of SSLs. Significant risk factors for SSLs included age ≥ 40, male sex, diabetes mellitus, and hypertension.

Multitarget Stool RNA Test for Colorectal Cancer Screening

Importance

Noninvasive tests for colorectal cancer screening must include sensitive detection of colorectal cancer and precancerous lesions. These tests must be validated for the intended-use population, which includes average-risk individuals 45 years or older.

Objective

To evaluate the sensitivity and specificity of a noninvasive, multitarget stool RNA (mt-sRNA) test (ColoSense) test compared with results from a colonoscopy.

Design, Setting, and Participants

This phase 3 clinical trial (CRC-PREVENT) was a blinded, prospective, cross-sectional study to support a premarket approval application for a class III medical device. A total of 8920 participants were identified online using social media platforms and enrolled from June 2021 to June 2022 using a decentralized nurse call center. All participants completed the mt-sRNA test, which incorporated a commercially available fecal immunochemical test (FIT), concentration of 8 RNA transcripts, and participant-reported smoking status. Stool samples were collected prior to participants completing a colonoscopy at their local endoscopy center. The mt-sRNA test results (positive or negative) were compared with index lesions observed on colonoscopy. Over the course of 12 months, individuals 45 years and older were enrolled in the clinical trial using the decentralized recruitment strategy. Participants were enrolled from 49 US states and obtained colonoscopies at more than 3800 different endoscopy centers.

Main Outcomes and Measures

The primary outcomes included the sensitivity of the mt-sRNA test for detecting colorectal cancer and advanced adenomas and the specificity for no lesions on colonoscopy.

Results

The mean (range) age of participants was 55 (45-90) years, with 4% self-identified as Asian, 11% as Black, and 7% as Hispanic. Of the 8920 eligible participants, 36 (0.40%) had colorectal cancer and 606 (6.8%) had advanced adenomas. The mt-sRNA test sensitivity for detecting colorectal cancer was 94%, sensitivity for detecting advanced adenomas was 46%, and specificity for no lesions on colonoscopy was 88%. The mt-sRNA test showed significant improvement in sensitivity for colorectal cancer (94% vs 78%; McNemar P = .01) and advanced adenomas (46% vs 29%; McNemar P < .001) compared with results of the FIT.

Conclusions and Relevance

In individuals 45 years and older, the mt-sRNA test showed high sensitivity for colorectal neoplasia (colorectal cancer and advanced adenoma) with significant improvement in sensitivity relative to the FIT. Specificity for no lesions on colonoscopy was comparable to existing molecular diagnostic tests.

Trial Registration

ClinicalTrials.gov Identifier: NCT04739722.

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.

Korean Guidelines for Postpolypectomy Colonoscopic Surveillance: 2022 revised edition

Colonoscopic polypectomy is effective in decreasing the incidence and mortality of colorectal cancer (CRC). Premalignant polyps discovered during colonoscopy are associated with the risk of metachronous advanced neoplasia. Postpolypectomy surveillance is the most important method for managing advanced metachronous neoplasia. A more efficient and evidence-based guideline for postpolypectomy surveillance is required because of the limited medical resources and concerns regarding colonoscopy complications. In these consensus guidelines, an analytic approach was used to address all reliable evidence to interpret the predictors of CRC or advanced neoplasia during surveillance colonoscopy. The key recommendations state that the high-risk findings for metachronous CRC following polypectomy are as follows: adenoma ≥10 mm in size; 3 to 5 (or more) adenomas; tubulovillous or villous adenoma; adenoma containing high-grade dysplasia; traditional serrated adenoma; sessile serrated lesion containing any grade of dysplasia; serrated polyp of at least 10 mm in size; and 3 to 5 (or more) sessile serrated lesions. More studies are needed to fully comprehend the patients who are most likely to benefit from surveillance colonoscopy and the ideal surveillance interval to prevent metachronous CRC.

Korean guidelines for postpolypectomy colonoscopic surveillance: 2022 revised edition

Colonoscopic polypectomy is effective in decreasing the incidence and mortality of colorectal cancer (CRC). Premalignant polyps discovered during colonoscopy are associated with the risk of metachronous advanced neoplasia. Postpolypectomy surveillance is the most important method for the management of advanced metachronous neoplasia. A more efficient and evidence-based guideline for postpolypectomy surveillance is required because of limited medical resources and concerns regarding colonoscopy complications. In these consensus guidelines, an analytic approach was used to address all reliable evidence to interpret the predictors of CRC or advanced neoplasia during surveillance colonoscopy. The key recommendations state that the high-risk findings for metachronous CRC following polypectomy are as follows: (1) adenoma ≥10 mm in size; (2) 3 to 5 (or more) adenomas; (3) tubulovillous or villous adenoma; (4) adenoma containing high-grade dysplasia; (5) traditional serrated adenoma; (6) sessile serrated lesion (SSL) containing any grade of dysplasia; (7) serrated polyp of at least 10 mm in size; and (8) 3 to 5 (or more) SSLs. More studies are needed to fully comprehend the patients most likely to benefit from surveillance colonoscopy and the ideal surveillance interval to prevent metachronous CRC.

[Korean Guidelines for Postpolypectomy Colonoscopic Surveillance: 2022 Revised Edition]

Colonoscopic polypectomy is effective in decreasing the incidence and mortality of colorectal cancer (CRC). Premalignant polyps discovered during colonoscopy are associated with the risk of metachronous advanced neoplasia. Postpolypectomy surveillance is the most important method for managing advanced metachronous neoplasia. A more efficient and evidence-based guideline for postpolypectomy surveillance is required because of the limited medical resources and concerns regarding colonoscopy complications. In these consensus guidelines, an analytic approach was used to address all reliable evidence to interpret the predictors of CRC or advanced neoplasia during surveillance colonoscopy. The key recommendations state that the high-risk findings for metachronous CRC following polypectomy are as follows: 1) adenoma ≥10 mm in size; 2) 3-5 (or more) adenomas; 3) tubulovillous or villous adenoma; 4) adenoma containing high-grade dysplasia; 5) traditional serrated adenoma; 6) sessile serrated lesion (SSL) containing any grade of dysplasia; 7) serrated polyp of at least 10 mm in size; and 8) 3-5 (or more) SSLs. More studies are needed to fully comprehend the patients who are most likely to benefit from surveillance colonoscopy and the ideal surveillance interval to prevent metachronous CRC.

The Genomic Landscape of Serrated Lesion of the Colorectum: Similarities and Differences With Tubular and Tubulovillous Adenomas

Serrated lesions of the colorectum are the precursors of 15-30% of colorectal cancers (CRCs). These lesions have a peculiar morphological appearance, and they are more difficult to detect than conventional adenomatous polyps. In this study, we sought to define the genomic landscape of these lesions using high-depth targeted sequencing. Eight sessile serrated lesions without dysplasia (SSL), three sessile serrated lesions with dysplasia (SSL/D), two traditional serrated adenomas (TSA), and three tubular adenomas (TA) were retrieved from the files of the Institute of Pathology of the University Hospital Basel and from the GILAB AG, Allschwil, Switzerland. Samples were microdissected together with the matched normal counterpart, and DNA was extracted for library preparation. Library preparation was performed using the Oncomine Comprehensive Assay targeting 161 common cancer driver genes. Somatic genetic alterations were defined using state-of-the-art bioinformatic analysis. Most SSLs, as well as all SSL/Ds and TSAs, showed the classical BRAF p.V600E mutation. The BRAF-mutant TSAs showed additional alterations in CTNNB1, NF1, TP53, NRAS, PIK3CA, while TA showed a consistently different profile, with mutations in ARID1A (two cases), SMAD4, CDK12, ERBB3, and KRAS. In conclusion, our results provide evidence that SSL/D and TSA are similar in somatic mutations with the BRAF hotspot somatic mutation as a major driver of the disease. On the other hand, TAs show a different constellation of somatic mutations such as ARID1A loss of function.

The Frontiers of Serrated Polyps

The serrated pathway of carcinogenesis has been the subject of intense investigation over the past 2 decades, but many gaps in our understanding still need to be resolved. Serrated polyp precursors include hyperplastic polyps, sessile serrated polyps, and traditional serrated adenomas. These are considered discrete entities, but there is emerging molecular data to suggest that they may be more closely related to each other than currently believed. The recent US Multi-Society Task Force surveillance guidelines for patients with serrated polyps are admittedly based on low quality evidence. In this brief review, we discuss the limitations in endoscopic detection and pathologic interpretation of serrated polyps and the implications of these diagnostic difficulties on risk prediction and postpolypectomy surveillance recommendations.

Application of Next Generation Quality/Statistical Process Control and Expert-Led Case Review to Increase the Consistency of Diagnostic Rates in Precancerous Colorectal Polyps

BACKGROUND

Prior work suggests high interrater variability in the pathologist diagnostic rate (PDR) of the precancerous polyp sessile serrated adenoma (SSA).

OBJECTIVES

To improve the diagnostic consistency in the pathological evaluation of colorectal polyp specimens with diagnostic rate awareness, using funnel plots (FPs)/control charts (CCs), and a focused group case review.

METHODS

All colorectal polyp specimen (CRPS) reports September 2015 to August 2017 were analyzed at one institution. PDRs were extracted using a hierarchical free-text string matching algorithm and visualized using FPs, showing pathologist specimen volume versus PDR, and CCs, showing pathologist versus normed PDR. The FPs/CCs were centered on the group median diagnostic rate (GMDR). Pathologists were shown their baseline SSA diagnostic rate in relation to the practice, and in January 2017, there was a focused group case review/open discussion of approximately 40 sequential cases signed as SSA with a gastrointestinal pathology expert.

RESULTS

Nine pathologists interpreted more than 250 CRPSs per year. FPs/CCs for the first and second years showed 6/4 and 3/1 P < .05/P < .001 pathologist outliers, respectively, in relation to the GMDR for SSA and 0/0 and 0/0 P < .05/P < .001 pathologist outliers, respectively, in relation to the GMDR for tubular adenoma (TA). An in silico kappa (ISK) for SSA improved from 0.52 to 0.62.

CONCLUSION

Diagnostic rate awareness facilitated by FPs/CCs coupled with focused expert-led reviews may help calibrate PDR. Variation in SSA PDRs still remains high in relation to TA. ISK represents an intuitive, useful metric and Next Generation Quality/Statistical Process Control a promising approach for objectively increasing diagnostic consistency.

Serrated polyps of the colon and rectum: a concise review

"Serrated polyps" is the term used for epithelial lesions of the colon and rectum that have a "sawtooth" pattern on the polyp's surface and crypt epithelium. The so-called serrated pathway describes the progression of sessile serrated adenomas and traditional serrated adenomas to colorectal cancer. Said pathway is well recognized as an alternative mechanism of carcinogenesis and accounts for 15-30% of the cases of colorectal cancer. It also explains a large number of the cases of interval colorectal cancer. Thus, due to their usually aggressive and uncertain behavior, serrated polyps are of the utmost importance in colorectal cancer screening. Our aim was to review the history, current nomenclature, pathophysiology, morphology, treatment, and surveillance of serrated polyps.

Correlation of Fecal Immunochemical Testing Levels With Pathology Results in a National Colorectal Cancer Screening Program

INTRODUCTION

Fecal immunochemical testing (FIT) positivity is determined by a threshold decided by individual screening programs. Data are limited on correlation between FIT levels and pathology identified at colonoscopy. Our aim was to examine the correlation between FIT levels and pathology identified in a national colorectal cancer screening program.

METHODS

FIT levels (n = 9,271) were analyzed and correlated with patient demographics and pathology identified, including adenomas, sessile serrated lesions, number/size of adenomas, and presence of dysplasia. Levels were divided into 2 categories: FIT levels were defined as "high" or "low" based on whether they were above or below the median (479 ngHb/mL). Multivariate analysis was performed.

RESULTS

A total of 8,084 patients (87%) underwent colonoscopy. Those younger than 65 years (odds ratio [OR] 1.267, 95% confidence interval [CI] 1.107-1.45, P = 0.001), those with an adenoma >10 mm (OR 1.736, 95% CI 01.512-1.991, P < 0.001), and those with left-sided adenomas (OR 1.484, 95% CI 1.266-1.74, P < 0.001) had higher FIT levels. Cancers (OR 2.8, 95% CI 2.09-3.75, P < 0.001) and high-grade dysplasia (OR 1.356, 95% CI 1.08-1.7, P = 0.008) had higher FIT levels, but varied greatly. The number of adenomas was not significant.

DISCUSSION

In this study, FIT levels were high for left-sided and large adenomas, suggesting that FIT has poor sensitivity for detection of diminutive and right-sided neoplasia. FIT levels had no association with gender and declined with age. Adenoma burden did not correlate with FIT levels; this is a novel finding. FIT levels vary greatly even in those with advanced neoplasia; therefore, FIT is unlikely to be useful as a risk stratification tool.

Interobserver agreement and the impact of mentorship on the diagnosis of inflammatory bowel disease-associated dysplasia among subspecialist gastrointestinal pathologists

The diagnosis of inflammatory bowel disease (IBD)-associated dysplasia is challenging, and past studies have demonstrated considerable interobserver variability in such diagnoses. This study aimed to assess interobserver agreement in IBD dysplasia diagnoses among subspecialty GI pathologists and to explore the impact of mentorship on diagnostic variability. Twelve GI pathologist mentees and 7 GI pathologist mentors reviewed 163 digitized slides. Participants rendered a diagnosis of negative for dysplasia, indefinite for dysplasia, low-grade dysplasia, or high-grade dysplasia and provided a confidence level for each case. Interobserver agreement and reliability were assessed using Cohen's and Fleiss' kappa (κ) statistics and intraclass correlation coefficient (ICC) analysis. The overall κ coefficient was 0.42 (95% CI: 0.38-0.46). The overall ICC was 0.67 (95% CI: 0.62-0.72). Κ coefficients ranged from 0.31 to 0.49 for mentor/mentee pairs and from 0.34 to 0.55 for pairs of mentees of the same mentor. The combined κ coefficient was 0.44 (95% CI: 0.39-0.48) for all mentees and 0.39 (95% CI: 0.34-0.43) for all mentors. Common features in low agreement cases included mucosal atrophy, areas of stark contrast, serrations, decreased goblet cells, absent surface epithelium, and poor orientation. Participants were confident in most diagnoses, and increased confidence levels generally correlated with higher interobserver agreement. Interobserver agreement among subspecialist GI pathologists in this curated cohort of IBD dysplasia cases was fair to moderate. Mentorship during GI pathology fellowship does not appear to be a significant factor contributing to interobserver variability, but increased experience also does not seem to improve interobserver agreement.

Hyperplastic polyp or sessile serrated lesion? The contribution of serial sections to reclassification

BACKGROUND

The histological discrimination of hyperplastic polyps from sessile serrated lesions can be difficult. Sessile serrated lesions and hyperplastic polyps are types of serrated polyps which confer different malignancy risks, and surveillance intervals, and are sometimes difficult to discriminate. Our aim was to reclassify previously diagnosed hyperplastic polyps as sessile serrated lesions or confirmed hyperplastic polyps, using additional serial sections.

METHODS

Clinicopathological data for all colorectal hyperplastic polyps diagnosed in 2016 and 2017 was collected. The slides were reviewed and classified as hyperplastic polyps, sessile serrated lesion, or other, using current World Health Organization criteria. Eight additional serial sections were performed for the confirmed hyperplastic polyp group and reviewed.

RESULTS

Of an initial 147 hyperplastic polyps from 93 patients, 9 (6.1%) were classified as sessile serrated lesions, 103 as hyperplastic polyps, and 35 as other. Of the 103 confirmed hyperplastic polyps, 7 (6.8%) were proximal, and 8 (7.8%) had a largest fragment size of ≥5 mm and < 10 mm. After 8 additional serial sections, 11 (10.7%) were reclassified as sessile serrated lesions. They were all less than 5 mm and represented 14.3% of proximal polyps and 10.4% of distal polyps. An average of 3.6 serial sections were required for a change in diagnosis.

CONCLUSION

Histopathological distinction between hyperplastic polyps and sessile serrated lesions remains a challenge. This study has uncovered a potential role for the use of additional serial sections in the morphological reappraisal of small hyperplastic polyps, especially when proximally located.

Gastric and small intestinal traditional serrated adenomas: a detailed morphologic and immunohistochemical analysis

BACKGROUND/AIMS

Traditional serrated adenomas (TSAs), despite their low incidence in colorectum, may originate in other parts of the gastrointestinal (GI) tract, including stomach and small intestine. Malignant transformation for upper GI TSAs has recently been reported in the literature. Here, we present a series of gastric and small intestinal TSAs with the aim to characterize their morphologic and immunophenotypic features as well as their neoplastic potential in a compartmental manner using digitalized images.

MATERIALS AND METHODS

The study comprised 12 GI polyps with TSA features-5 gastric and 7 small intestinal. The extent of the characteristic features of TSA, including eosinophilic cells, ectopic crypt foci (ECF), slit-like serration, foveolar epithelium, goblet cells, together with dysplastic-carcinomatous foci were assessed on digitalized H-E images and were used as reference for immunohistochemical analysis.

RESULTS

All polyps in the cohort contained eosinophilic cells as the most extensive morphologic feature followed by ECF and slit-like serration in decreasing order. Serrated dysplasia was more common in gastric polyps, which more frequently showed neoplastic progression compared with the intestinal ones. CK20 was the most widely expressed marker with a preference to eosinophilic cells while ECFs were mostly negative. Ki67 showed the opposite pattern of CK20. MUC6 and MUC2 were selectively expressed in the basal zone and goblet cells, respectively.

CONCLUSION

Our results showed that the presence of eosinophilic cells with pencillate nuclei commonly accompanied by ECF and slit-like serration are the defining features of gastric and small intestinal TSAs. They frequently harbor neoplastic foci, particularly in gastric location where serrated dysplasia seems to be more common.

Terminology, Molecular Features, Epidemiology, and Management of Serrated Colorectal Neoplasia

In addition to the adenoma to carcinoma sequence, colorectal carcinogenesis can occur via the serrated pathway. Studies have focused on clarification of categories and molecular features of serrated polyps, as well as endoscopic detection and risk assessment. Guidelines from the World Health Organization propose assigning serrated polyps to categories of hyperplastic polyps, traditional serrated adenomas, and sessile serrated lesions (SSLs). Traditional serrated adenomas and SSLs are precursors to colorectal cancer. The serrated pathway is characterized by mutations in RAS and RAF, disruptions to the Wnt signaling pathway, and widespread methylation of CpG islands. Epidemiology studies of serrated polyps have been hampered by inconsistencies in terminology and reporting, but the prevalence of serrated class polyps is 20%-40% in average-risk individuals; most serrated polyps detected are hyperplastic. SSLs, the most common premalignant serrated subtype, and are found in up to 15% of average-risk patients by high-detecting endoscopists. Variations in rate of endoscopic detection of serrated polyps indicate the need for careful examination, with adequate bowel preparation and sufficient withdrawal times. Risk factors for SSLs include white race, family history of colorectal cancer, smoking, and alcohol intake. Patients with serrated polyps, particularly SSLs and traditional serrated adenomas, have an increased risk of synchronous and metachronous advanced neoplasia. Surveillance guidelines vary among countries, but SSLs and proximal hyperplastic polyps require special attention in assignment of surveillance interval-especially in light of concerns regarding incomplete detection and resection.

Traditional serrated adenoma: an overview of pathology and emphasis on molecular pathogenesis

Objective

To provide an overview of the pathology and molecular pathogenesis of traditional serrated adenomas (TSA).

Design

Describe the morphology and molecules that play a role in their pathogenesis.

Results

These exuberant polypoid lesions are typified by tall cells with deeply eosinophilic cytoplasm, elongated nuclei bearing delicate chromatin, ectopic crypt foci, deep clefting of the lining mucosa and an overall resemblance to small bowel mucosa.

Broadly, TSAs arise via three mechanisms. They may be BRAF mutated and CpG island methylator phenotype (CIMP)-high: right sided, mediated through a microvesicular hyperplastic polyp or a sessile serrated adenoma, may also have RNF43 mutations and result in microsatellite stable (MSS) colorectal cancers (CRC). The second pathway that is mutually exclusive of the first is mediated through KRAS mutation with CIMP-low TSAs. These are left-sided TSAs, are not associated with another serrated polyp and result in MSS CRC. These TSAs also have RSPO3, RNF43 and p53 mutations together with aberrant nuclear localisation of β-catenin. Third, there is a smaller group of TSAs that are BRAF and KRAS wild type and arise by as yet unknown molecular events. All TSAs show retention of mismatch repair proteins.

Conclusion

These are characteristic unusual polyps with a complex molecular landscape.

Clinicopathological factors associated with BRAF-V600E mutation in colorectal serrated adenomas

Serrated adenomas are genetically heterogeneous, and the histological classification into sessile serrated (SSA) adenoma and traditional serrated adenoma (TSA) does not reflect the molecular landscape. The objective of this study was to assess clinical or pathological factors associated with BRAF-V600E mutation in serrated adenomas. Systematic review and meta-analysis was performed by searching electronic databases from January 2011 to January 2019 for studies assessing the association of BRAF-V600E mutation with clinical or pathological features of serrated adenomas. Odds ratio (OR) was calculated for each factor; a P-value <0.05 was considered significant. Forty studies assessing 3511 serrated adenomas (2375 SSAs and 1136 TSAs) were included. BRAF-V600E mutation was significantly associated with proximal localisation (OR = 2.71; P < 0.00001) and CIMP-H status (OR = 4.81; P < 0.0001) in both SSA and TSA, with polyp size <10 mm (OR = 0.41; P = 0.02) in TSA, and with endoscopic pit pattern II-O (OR = 13.11; P < 0.00001) and expression of MUC5A5 (OR = 4.43; P = 0.003) and MUC6 (OR = 2.28; P < 0.05) in SSA. Conversely, BRAF mutation was not associated with age <70 years (OR = 1.63; P = 0.34), age <60 years (OR = 0.86; P = 0.79), female sex (OR = 0.77; P = 0.12), flat morphology (OR = 1.52; P = 0.16), presence of any dysplasia (OR = 1.01; P = 0.59), serrated dysplasia (OR = 1.23; P = 0.72) and invasive cancer (OR = 0.67; P = 0.32), nuclear β-catenin expression (OR = 0.73; P = 0.21) and p53 overexpression (OR = 1.24; P = 0.82). In conclusion, BRAF-V600E mutation is associated with proximal localisation and CIMP-H status in both SSA and TSA, with size <10 mm only in TSA, and with expression of MUC5A5 and MUC6 and endoscopic pit pattern II-O at least in SSA. In serrated adenomas, BRAF-V600E mutation does not seem to be associated with age and sex, with the prevalence of dysplasia and cancer and with the morphology of the dysplastic component.

Serrated lesions of the colon A window on a more clear classification

Serrated polyps evaluation represents a challenge for pathologists for lacking of univocal criteria that leads to different inter -individual interpretation. The aim of our review is to offer an alternative simpler histologic and endoscopic approach to these lesions for a more correct relationship between endoscopists and pathologists.

Serrated Polyps of Colon and Rectum: a Clinicopathologic Review

BACKGROUND

In the past decade, there have been significant changes in the classification and nomenclature of colorectal polyps. Previously, only two groups of lesions were widely recognized, the adenoma and the hyperplastic polyp. Adenomas were considered the only precursor of colorectal cancer, and hyperplastic polyps were considered innocent with no malignant potential. However, recent discoveries about molecular pathways of colorectal cancers have significantly changed our understanding of these neoplasms. Serrated polyps-previously uniformly called hyperplastic polyps-are now known to comprise a heterogeneous family of neoplasms united by their characteristic saw tooth morphology but differing in many important ways, including their malignant potential and molecular profile. This group of neoplasms includes both hyperplastic polyps and the more recently recognized serrated adenomas. Serrated adenomas can be subdivided into the traditional serrated adenoma and the sessile serrated adenoma/polyp. Both of these lesions show characteristic molecular changes, which differ from traditional colorectal adenomatous polyps.

OBJECTIVES

In this review, we will discuss the morphologic features of serrated colorectal lesions, the molecular alterations that characterize them, and their role in colorectal cancer development.

MATERIAL AND METHODS

The English literature regarding the new nomenclature will be reviewed and the key diagnostic points will be recorded.

RESULTS AND DISCUSSION

This large group of polyps has recently been better classified which needs specific attention by pathologists, gastroenterologists and even surgeons.

Active BRAF-V600E is the key player in generation of a sessile serrated polyp-specific DNA methylation profile

BACKGROUND

Sessile serrated polyps (SSPs) have emerged as important precursors for a large number of sporadic colorectal cancers. They are difficult to detect during colonoscopy due to their flat shape and the excessive amounts of secreted mucin that cover the polyps. The underlying genetic and epigenetic basis for the emergence of SSPs is largely unknown with existing genetic studies confined to a limited number of oncogenes and tumor suppressors. A full characterization of the genetic and epigenetic landscape of SSPs would provide insight into their origin and potentially offer new biomarkers useful for detection of SSPs in stool samples.

METHODS

We used a combination of genome-wide mutation detection, exome sequencing and DNA methylation profiling (via methyl-array and whole-genome bisulfite sequencing) to analyze multiple samples of sessile serrated polyps and compared these to familial adenomatous polyps.

RESULTS

Our analysis revealed BRAF-V600E as the sole recurring somatic mutation in SSPs with no additional major genetic mutations detected. The occurrence of BRAF-V600E was coincident with a unique DNA methylation pattern revealing a set of DNA methylation markers showing significant (~3 to 30 fold) increase in their methylation levels, exclusively in SSP samples. These methylation patterns effectively distinguished sessile serrated polys from adenomatous polyps and did so more effectively than parallel gene expression profiles.

CONCLUSIONS

This study provides an important example of a single oncogenic mutation leading to reproducible global DNA methylation changes. These methylated markers are specific to SSPs and could be of important clinical relevance for the early diagnosis of SSPs using non-invasive approaches such as fecal DNA testing.

Management of Serrated Polyps of the Colon

PURPOSE OF REVIEW

The purpose of this review is to summarize the management of serrated colorectal polyps (SPs), with a particular focus on the most common premalignant SP, sessile serrated adenoma or polyp (SSA/P). These lesions present a challenge for endoscopists with respect to detection and resection, and are also susceptible to pathologic misdiagnosis.

RECENT FINDINGS

Patients with SSA/Ps are at an increased risk of future colorectal neoplasia, including advanced polyps and cancer. Reasonable benchmarks for SP detection rates are 5-7% for SSA/Ps and 10-12% for proximal SPs. Certain endoscopic techniques such as chromoendoscopy, narrow band imaging, water immersion, and wide-angle viewing may improve SSA/P detection. Emerging endoscopic techniques such as underwater polypectomy, suction pseudopolyp technique, and piecemeal cold snare polypectomy are helpful tools for the endoscopist's armamentarium for removing SSA/Ps. Proper orientation of SSA/P specimens can improve the accuracy of pathology readings. Patients with confirmed SSA/Ps and proximal HPs should undergo surveillance at intervals similar to what is recommended for patients with conventional adenomas. Patients with SSA/Ps may also be able to lower their risk of future polyps by targeting modifiable risk factors including tobacco and alcohol use and high-fat diets. NSAIDs and aspirin appear to be protective agents. SPs and SSA/Ps in particular are important colorectal cancer precursors that merit special attention to ensure adequate detection, resection, and surveillance.

British Society of Gastroenterology position statement on serrated polyps in the colon and rectum

Serrated polyps have been recognised in the last decade as important premalignant lesions accounting for between 15% and 30% of colorectal cancers. There is therefore a clinical need for guidance on how to manage these lesions; however, the evidence base is limited. A working group was commission by the British Society of Gastroenterology (BSG) Endoscopy section to review the available evidence and develop a position statement to provide clinical guidance until the evidence becomes available to support a formal guideline. The scope of the position statement was wide-ranging and included: evidence that serrated lesions have premalignant potential; detection and resection of serrated lesions; surveillance strategies after detection of serrated lesions; special situations-serrated polyposis syndrome (including surgery) and serrated lesions in colitis; education, audit and benchmarks and research questions. Statements on these issues were proposed where the evidence was deemed sufficient, and re-evaluated modified via a Delphi process until >80% agreement was reached. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) tool was used to assess the strength of evidence and strength of recommendation for finalised statements. Key recommendation: we suggest that until further evidence on the efficacy or otherwise of surveillance are published, patients with sessile serrated lesions (SSLs) that appear associated with a higher risk of future neoplasia or colorectal cancer (SSLs ≥10 mm or serrated lesions harbouring dysplasia including traditional serrated adenomas) should be offered a one-off colonoscopic surveillance examination at 3 years (weak recommendation, low quality evidence, 90% agreement).

Optical Diagnosis of Sessile Serrated Polyps: Bottleneck for the Optical Diagnosis Paradigm?

BACKGROUND

Optical diagnosis of diminutive (1 to 5 mm) polyps could result in a more cost-effective colonoscopy practice. Previous optical diagnosis studies did not incorporate the differentiation of sessile serrated polyps (SSPs). This study aimed to evaluate the impact of optical diagnosis of diminutive SSPs on the overall performance of endoscopic polyp differentiation in daily colonoscopy practice.

METHODS

Endoscopy data were prospectively collected between 2011 and 2014 in a colonoscopy center. Each endoscopist reported a real-time optical diagnosis (SSP, adenoma or hyperplastic polyp) for all lesions in a structured colonoscopy reporting system, using narrow band imaging at their discretion. Study outcomes were accuracy of optical diagnosis, surveillance interval agreement and negative predictive value for diminutive rectosigmoid neoplastic histology based on the optical diagnosis of diminutive polyps compared to histopathology.

RESULTS

Of 2853 removed diminutive polyps, 202 (7.1%) were histologically proven SSPs. Optical diagnosis of diminutive SSPs was accurate in 24.4%. Diminutive SSPs determined 6.9% of postpolypectomy surveillance assignments. Inaccurate optical diagnosis of diminutive SSPs led to lower surveillance interval agreement (78.1% vs. 53.3%, P<0.01) and pooled negative predictive value per polyp (84.3% vs. 50.0%; P<0.01) in patients with diminutive SSPs when compared to patients without diminutive SSPs. Accurate endoscopic identification of diminutive SSPs improved from 0% in 2011 to 47% in 2014 (P=0.02).

CONCLUSIONS

Endoscopic characterization of diminutive SSPs is difficult, impairing overall performance of optical diagnosis in patients with diminutive SSPs. Future optical diagnosis studies should use validated trainings and classification algorithms that include differentiation of SSPs.

Endoscopic mucosal resection for large serrated lesions in comparison with adenomas: a prospective multicentre study of 2000 lesions

OBJECTIVE

Endoscopic mucosal resection (EMR) is effective for large laterally spreading flat and sessile lesions (LSLs). Sessile serrated adenomas/polyps (SSA/Ps) are linked to the relative failure of colonoscopy to prevent proximal colorectal cancer. We aimed to examine the technical success, adverse events and recurrence following EMR for large SSA/Ps in comparison with large conventional adenomas.

DESIGN

Over 74 months till August 2014, prospective multicentre data of LSLs ≥20 mm were analysed. A standardised dye-based conventional EMR technique followed by scheduled surveillance colonoscopy was used.

RESULTS

From a total of 2000 lesions, 323 SSA/Ps in 246 patients and 1527 adenomas in 1425 patients were included for analysis. Technical success for EMR was superior in SSA/Ps compared with adenomas (99.1% vs 94.5%, p<0.001). Significant bleeding and perforation were similar in both cohorts. The cumulative recurrence rates for adenomas after 6, 12, 18 and 24 months were 16.1%, 20.4%, 23.4% and 28.4%, respectively. For SSA/Ps, they were 6.3% at 6 months and 7.0% from 12 months onwards (p<0.001). Following multivariable adjustment, the HR of recurrence for adenomas versus SSA/Ps was 1.7 (95% CI 0.9 to 3.0, p=0.097). Subgroup analysis by lesion size revealed an eightfold increased risk of recurrence for 20-25 mm adenomas versus SSA/Ps, but no significantly different risk between lesion types in larger lesion groups.

CONCLUSION

Recurrence after EMR of 20-25 mm LSLs is significantly less frequent in SSA/Ps compared with adenomatous lesions. SSA/Ps can be more effectively removed than adenomatous LSLs with equivalent safety. Ensuring complete initial resection is imperative for avoiding recurrence.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT01368289.

Clinical risk factors of colorectal cancer in patients with serrated polyposis syndrome: a multicentre cohort analysis

OBJECTIVE

Serrated polyposis syndrome (SPS) is accompanied by an increased risk of colorectal cancer (CRC). Patients fulfilling the clinical criteria, as defined by the WHO, have a wide variation in CRC risk. We aimed to assess risk factors for CRC in a large cohort of patients with SPS and to evaluate the risk of CRC during surveillance.

DESIGN

In this retrospective cohort analysis, all patients with SPS from seven centres in the Netherlands and two in the UK were enrolled. WHO criteria were used to diagnose SPS. Patients who only fulfilled WHO criterion-2, with IBD and/or a known hereditary CRC syndrome were excluded.

RESULTS

In total, 434 patients with SPS were included for analysis; 127 (29.3%) were diagnosed with CRC. In a per-patient analysis ≥1 serrated polyp (SP) with dysplasia (OR 2.07; 95% CI 1.28 to 3.33), ≥1 advanced adenoma (OR 2.30; 95% CI 1.47 to 3.67) and the fulfilment of both WHO criteria 1 and 3 (OR 1.60; 95% CI 1.04 to 2.51) were associated with CRC, while a history of smoking was inversely associated with CRC (OR 0.36; 95% CI 0.23 to 0.56). Overall, 260 patients underwent surveillance after clearing of all relevant lesions, during which two patients were diagnosed with CRC, corresponding to 1.9 events/1000 person-years surveillance (95% CI 0.3 to 6.4).

CONCLUSION

The presence of SPs containing dysplasia, advanced adenomas and/or combined WHO criteria 1 and 3 phenotype is associated with CRC in patients with SPS. Patients with a history of smoking show a lower risk of CRC, possibly due to a different pathogenesis of disease. The risk of developing CRC during surveillance is lower than previously reported in literature, which may reflect a more mature multicentre cohort with less selection bias.

Colorectal cancer anatomic distribution patterns remain the same after sessile serrated adenoma/polyp considered cancer precursor: a 9-year comparison study from community-based endoscopy centers

BACKGROUND

The overall incidence of colorectal cancer (CRC) in the United States has steadily decreased. However, the incidence of right-sided CRC remains unchanged for the past two decades. The serrated neoplastic pathway (sessile serrated adenoma/polyp, SSA/P) has been considered an important pathway of colorectal carcinogenesis, especially in the right-sided CRC. The aim of this study was to compare CRC anatomic distribution patterns in a 9-year interval in the general population before and after SSA/P was recognized and treated as a CRC precursor.

METHODS

The Miraca Life Sciences (MLS) pathology database was queried for all primary CRCs diagnosed between 8/3/2000 to 12/31/2005 (control group) and 1/1/2014 to 12/31/2014 (current group). Patients' demographics, clinical information, and pathology reports were collected and analyzed.

RESULTS

A total of 5,602 patients with 5,685 CRCs were identified, of which 2,728 patients with 2,765 CRCs in current group and 2,874 patients with 2,920 CRCs in control group. Overall, there were no statistical differences in the current group in regards to the anatomical distribution patterns of CRCs in the proximal, right-sided, distal, and left-sided colon or genders compared with the control group (all P>0.05). Among the current group, there were 33 (1.2%) patients with 38 (1.4%) CRCs arising in SSA/Ps [serrated carcinomas (SCAs)], of which 33 (86.8%) were in the right-sided colon and 5 (13.2%) in the left-sided colon. Twenty-three (69.7%) SCA patients were female with significant advanced age than male (76.4 vs. 69.6, P=0.023).

CONCLUSIONS

The overall current CRC anatomic distribution patterns after SSA/Ps managed as CRC precursor remain the same in the patients' population from the community-based endoscopy centers in the U.S. It is suggested that the current SSA/P management might need to be further modified.

Impact of reassessment of colonic hyperplastic polyps by expert GI pathologists

BACKGROUND

Recommended follow-up intervals after endoscopic removal of hyperplastic polyps (HP) and sessile serrated adenomas (SSA) differ because of assumed differences in biological behaviour. However, histopathologic differentiation is difficult, with higher SSA rates reported from specialist GI histopathologists.

OBJECTIVE

The objective of this study was to clarify the relevance of histologic reassessment of HP.

DESIGN AND SETTING

From a prospective screening colonoscopy study relevant serrated lesions (excluding distal small HP ≤5 mm) diagnosed by private practice pathologists were reassessed by four specialized GI pathologists

PATIENTS

One thousand sixty-nine screening colonoscopies were performed in patients.

MAIN OUTCOME MEASUREMENTS

In terms of main outcome measurements, there is a likelihood of changes of the HP diagnosis on reassessment, as well as interrater variability.

RESULTS

SSA were initially diagnosed in 7 cases (0.7%) and relevant HP in 83 (7.8%; 101 lesions). Of the latter, the chance of a change in diagnosis from HP to SSA by any of the four specialist histopathologists was higher for larger (>5 mm) and right-sided lesions (19.1 vs 1.3%, OR 18.4, p = 0.04) including a higher likelihood to change recommended follow-up intervals (32.1 vs 3.3%, p < 0.01). However, follow-up intervals were determined by concomitant adenomas in 41%. Interrater variability was also higher for these lesions (p = 0.04), with an overall kappa value of 0.48. However, this issue related to only 1.2% of the 1069 study cases.

LIMITATION

The limitations this study are the limited case number as well as limited retrospective assessment.

CONCLUSIONS

Right-sided HP >5 mm had a higher chance of change in diagnosis to SSA; therefore, they should probably be treated like adenomas and be removed. However, reliable data for recommendations on follow-up intervals of HP or SSA will require follow-up studies.

Clinical and endoscopic predictors of cytological dysplasia or cancer in a prospective multicentre study of large sessile serrated adenomas/polyps

OBJECTIVE

The serrated neoplasia pathway accounts for up to 30% of all sporadic colorectal cancers (CRCs). Sessile serrated adenomas/polyps (SSA/Ps) with cytological dysplasia (SSA/P-D) are a high-risk serrated CRC precursor with little existing data. We aimed to describe the clinical and endoscopic predictors of SSA/P-D and high grade dysplasia (HGD) or cancer.

DESIGN

Prospective multicentre data of SSA/Ps ≥20 mm referred for treatment by endoscopic mucosal resection (September 2008-July 2013) were analysed. Imaging and lesion assessment was standardised. Histological findings were correlated with clinical and endoscopic findings.

RESULTS

268 SSA/Ps were found in 207/1546 patients (13.4%). SSA/P-D comprised 32.4% of SSA/Ps ≥20 mm. Cancer occurred in 3.9%. On multivariable analysis, SSA/P-D was associated with increasing age (OR=1.69 per decade; 95% CI (1.19 to 2.40), p0.004) and increasing lesion size (OR=1.90 per 10 mm; 95% CI (1.30 to 2.78), p0.001), an 'adenomatous' pit pattern (Kudo III, IV or V) (OR=3.98; 95% CI (1.94 to 8.15), p<0.001) and any 0-Is component within a SSA/P (OR=3.10; 95% CI (1.19 to 8.12) p0.021). Conventional type dysplasia was more likely to exhibit an adenomatous pit pattern than serrated dysplasia. HGD or cancer was present in 7.2% and on multivariable analysis, was associated with increasing age (OR=2.0 per decade; 95% CI 1.13 to 3.56) p0.017) and any Paris 0-Is component (OR=10.2; 95% CI 3.18 to 32.4, p<0.001).

CONCLUSIONS

Simple assessment tools allow endoscopists to predict SSA/P-D or HGD/cancer in SSA/Ps ≥20 mm. Correct prediction is limited by failure to recognise SSA/P-D which may mimic conventional adenoma. Understanding the concept of SSA/P-D and the pitfalls of SSA/P assessment may improve detection, recognition and resection and potentially reduce interval cancer.

TRIAL REGISTRATION NUMBER

NCT01368289.

Inflammatory response in serrated precursor lesions of the colon classified according to WHO entities, clinical parameters and phenotype-genotype correlation

Studies on traditional serrated adenoma (TSA) and sessile serrated adenoma with dysplasia (SSA‐D) are rare due to the low frequency of these lesions, which are well defined by the latest WHO classification. However, introducing new morphological criteria such as intra‐epithelial lymphocytes (IELs) might facilitate colorectal polyp diagnoses. Additionally, the phenotype–genotype correlation needs to be updated as the terminology has repeatedly changed. This study analysed 516 polyps, consisting of 118 classical adenomas (CAD), 116 hyperplastic polyps (HPP), 179 SSAs, 41 SSA‐Ds, and 62 TSAs. The lesions were analysed in relation to the patients’ clinical parameters including gender, age, localisation, and size. The inflammatory background of the polyps was quantified and BRAF and KRAS mutations as well as MLH1 and CDKN2A promoter methylation were assessed. In multivariate analyses, an increase in IELs was an independent and robust new criterion for the diagnosis of SSA‐D (p < 0.001). Superficial erosions and acute neutrophil granulocytes led to reactive changes potentially resembling dysplasia. KRAS and BRAF mutations were associated with CAD/TSA and HPP/SSA, respectively. However, almost half of TSAs had a BRAF mutation and were KRAS wild type. CDKN2A seems to precede MLH1 hyper‐methylation within the serrated carcinogenesis model. The genotyping of WHO‐based entities – and especially SSA – has sharpened in comparison to previously published data. TSAs can be sub‐grouped according to their mutation status. Of note, the higher number of IELs in SSA‐D reflects their close relationship to colorectal cancers with micro‐satellite instability. Therefore, IELs might represent a new diagnostic tool for SSA‐D.

The serrated neoplasia pathway of colorectal tumors: Identification of MUC5AC hypomethylation as an early marker of polyps with malignant potential

The serrated neoplasia pathway accounts for 20-30% of colorectal cancers (CRC), which are characterized by extensive methylation (CpG island methylation phenotype, CIMP), frequent BRAF mutation and high microsatellite instability (MSI). We recently identified MUC5AC mucin gene hypomethylation as a specific marker of MSI CRC. The early identification of preneoplastic lesions among serrated polyps is currently challenging. Here, we performed a detailed pathological and molecular analysis of a large series of colorectal serrated polyps and evaluated the usefulness of mucin genes MUC2 and MUC5AC to differentiate serrated polyps and to identify lesions with malignant potential. A series of 330 colorectal polyps including 218 serrated polyps [42 goblet cell-rich hyperplastic polyps (GCHP), 68 microvesicular hyperplastic polyps (MVHP), 100 sessile serrated adenoma (SSA) and eight traditional serrated adenoma (TSA)] and 112 conventional adenomas was analyzed for BRAF/KRAS mutations, MSI, CIMP, MLH1 and MGMT methylation, and MUC2 and MUC5AC expression and methylation. We show that MUC5AC hypomethylation is an early event in the serrated neoplasia pathway, and specifically detects MVHP and SSA, arguing for a filiation between MVHP, SSA and CIMP-H/MSI CRC, whereas GCHP and TSA arise from a distinct pathway. Moreover, MUC5AC hypomethylation specifically identified serrated lesions with BRAF mutation, CIMP-H or MSI, suggesting that it may be useful to identify serrated neoplasia pathway-related precursor lesions. Our data suggest that MVHP should be recognized among HP and require particular attention.

UK guidance for the pathological reporting of serrated lesions of the colorectum

Bowel cancer screening programmes have highlighted to endoscopists and clinicians the spectrum of serrated colorectal lesions. One of the most significant developments has been the recognition that sessile serrated lesions (SSLs), while bearing histological resemblance to hyperplastic polyps (HPs), may be associated with the enhanced development of epithelial dysplasia and colorectal adenocarcinoma. Different minimum criteria exist for the diagnosis of SSLs and their differentiation from HPs. Furthermore, the spectrum of terminology used to describe the entire range of serrated lesions is wide. This variability has impaired interobserver agreement during their histopathological assessment. Here, we provide guidance for the histopathological reporting of serrated lesions, including a simplified nomenclature system. Essentially, we recommend use of the following terms: HP, SSL, SSL with dysplasia, traditional serrated adenoma (TSA) and mixed polyp. It is hoped that this standardisation of nomenclature will facilitate studies of the biological significance of serrated lesions in terms of the relative risk of disease progression.

Endoscopic and histologic characteristics of serrated lesions

In recent years, a second pathway for colonic carcinogenesis, distinct from the adenomatous pathway, has been explored. This is referred to as serrated pathway and includes three types of polyp, characterised by a serrated appearance of the crypts: hyperplastic polyps (HP), sessile serrated adenomas (SSA) or lesions, and traditional serrated adenomas. Each lesion has its own genetic, as well as macroscopic and microscopic morphological features. Because of their flat aspect, their detection is easier with chromoendoscopy (carmin indigo or narrow-band imaging). However, as we show in this review, the distinction between SSA and HP is quite difficult. It is now recommended to resect in one piece as it is possible the serrated polyps with a control in a delay depending on the presence or not of dysplasia. These different types of lesion are described in detail in the present review in general population, in polyposis and in inflammatory bowel diseases patients. This review highlights the need to improve characterization and understanding of this way of colorectal cancerogenesis.

Sessile serrated polyp prevalence determined by a colonoscopist with a high lesion detection rate and an experienced pathologist

BACKGROUND

The prevalence of sessile serrated adenomas and/or polyps (SSA/Ps) is uncertain.

OBJECTIVE

To determine the prevalence of SSA/Ps and SSA/Ps with cytologic dysplasia (SSA/P-CD) by using a colonoscopist with a high lesion detection rate and an expert in serrated lesion pathology.

DESIGN

Retrospective screening colonoscopy study.

SETTING

Academic endoscopy unit.

PATIENTS

A total of 1910 average risk, asymptomatic patients aged ≥50 years underwent screening colonoscopy between August 2005 and April 2012 by a single colonoscopist with a high lesion detection rate.

INTERVENTIONS

Slides of all lesions in the serrated class proximal to the sigmoid colon and all rectal and sigmoid colon serrated lesions >5 mm in size were reviewed by an experienced GI pathologist.

MAIN OUTCOME MEASUREMENTS

Prevalence of SSA/Ps, defined as the proportion of patients with ≥1 SSA/P.

RESULTS

There were 1910 patients, of whom 389 had 656 lesions in the serrated class. Review by the experienced GI pathologist determined a prevalence of SSA/Ps without cytologic dysplasia of 7.4% and SSA/Ps-CD of 0.6% (total SSA/P prevalence 8.1%). SSA/Ps and SSA/Ps-CD comprised 5.6% and 0.3%, respectively, of all resected polyps. The mean size of SSA/Ps was 7.13 mm (standard deviation [SD] 4.66), and 51 of 77 (66.2%) polyps ≥10 mm in the serrated class were SSA/Ps.

LIMITATIONS

Retrospective design.

CONCLUSION

A colonoscopist with a high lesion detection rate and an experienced pathologist identified a high prevalence (8.1%) of SSA/Ps in a screening population. SSA/Ps are more common than previously believed.

Sessile serrated adenomas: an evidence-based guide to management

The concept of serrated colorectal neoplasia and a serrated pathway to colorectal cancer (CRC) is relatively new and continuing to evolve, but it has become highly relevant to gastroenterologists, pathologist, and oncologists alike. Sessile serrated adenomas (SSA) are now thought to be the major precursor lesion of serrated pathway cancers, which represent up to one-third of all sporadic CRC cases. However, despite their increasingly recognized importance, relatively little is known about the epidemiology and natural history of SSAs, and the molecular and epigenetic aspects are incompletely understood. Endoscopists must be aware of the unique features of SSAs so that the practice of colonoscopic screening for CRC can include optimized detection, removal, and appropriate surveillance of SSAs and other serrated precursor lesions. In this review, we discuss the history, epidemiology, and pathologic aspects of SSAs, as well as a recommended management approach and a discussion of uncertainties and opportunities for future research.

Serrated and non-serrated precursor lesions of colorectal cancer

Although often viewed as a single disease, colorectal cancer more accurately represents a family of diseases with different precursor lesions. Conventional (tubular, tubulovillous and villous) adenomas are the most common neoplastic lesions occurring in the large intestine. They have adenomatous polyposis coli (APC) mutations and arise from dysplastic aberrant crypt foci, initially as polyclonal lesions. In sporadic tumours, neoplastic progression follows the traditional pathway (chromosomal instability pathway), resulting in CpG island methylator phenotype (CIMP)-negative, microsatellite-stable (MSS), BRAF and KRAS wild-type cancers. Germline mutations in the APC gene lead to familial adenomatous polyposis. Conventional adenomas are also the precursors of Lynch syndrome-associated microsatellite-instable (MSI-high) cancers. Sessile serrated adenoma/polyp (SSA/P) is the principal precursor lesion of the serrated pathway, in which BRAF mutation can lead to colorectal cancer with MSI-high CIMP-high or MSS CIMP-high phenotype. SSA/Ps have been associated with synchronous and metachronous invasive adenocarcinomas as well as so-called interval carcinomas. Serrated polyposis is rare but most likely underdiagnosed. Affected individuals bear an increased but unspecified risk for the development of colorectal cancer; close endoscopic surveillance is warranted. Traditional serrated adenomas (TSAs) are much less common than the other serrated lesions. Cancers originating from TSAs may show KRAS mutation with a CIMP-high MSS phenotype.

Pathology of serrated colorectal lesions

The concept of serrated colorectal neoplasia has become recognised as a key process in the development of colorectal cancer (CRC) and an important alternative pathway to malignancy compared with the long established ‘adenoma-carcinoma’ sequence. Increasing recognition of the morphological spectrum of serrated lesions has occurred in parallel with elucidation of the distinct molecular genetic characteristics of progression from normal mucosa, via the ‘serrated pathway’, to CRC. Some of these lesions can be difficult to identify at colonoscopy. Challenges for pathologists include the requirement for accurate recognition of the forms of serrated lesions that are associated with a significant risk of malignant progression and therefore the need for widely disseminated reproducible criteria for their diagnosis. Alongside this process, pathologists and endoscopists need to formulate clear guidelines for the management of patients with these lesions, particularly with respect to the optimal follow-up intervals. This review provides practical guidance for the recognition of these lesions by pathologists, a discussion of ‘serrated adenocarcinoma’ and an insight into the distinct molecular genetic alterations that are seen in this spectrum of lesions in comparison to those that characterise the classic ‘adenoma-carcinoma’ sequence.

The significance of ectopic crypt formation in the differential diagnosis of colorectal polyps

Background

Ectopic crypts, defined as abnormally positioned crypts that have lost their orientation toward the muscularis mucosae, have been suggested to be the best defining histologic feature of traditional serrated adenoma (TSA). However, the significance of ectopic crypt formation (ECF) in the distinction between TSA and conventional adenoma (CA) has rarely been studied.

Methods

We designed this study to determine if ECF can be found in CA and its presence is exclusive to TSA. We studied 107 TSAs and 191 CAs including 106 tubular adenomas (TAs), 66 tubulovillous adenomas (TVAs), and 19 villous adenomas (VAs).

Results

ECF was identified in most (79.4%) but not all TSAs. Additionally, ECF was not infrequent in CA (62 of 191, 32.5%), and its presence correlated with the presence of a villous component and larger tumor size (each p <0.001).

Conclusions

Based on its strong association with the presence of a villous component and larger tumor size, ECF appears to be involved in the protuberant growth of colorectal CA. Because ECF can be found in CA, particularly in cases with a villous component, the possibility of CA should be considered before making a diagnosis of TSA when encountering colorectal polyps with ECF.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_212

Annexin A10 expression correlates with serrated pathway features in colorectal carcinoma with microsatellite instability

Annexin A10 (ANXA10) has recently been identified as a marker of sessile serrated adenomas/polyps of the colorectum. Although the serrated neoplasia pathway is thought to be involved in the majority of microsatellite instability-high (MSI-H) sporadic colorectal carcinomas (CRCs), the clinicopathological implications of ANXA10 expression in CRC are unknown. Here, we evaluated ANXA10 expression status in 168 MSI-H CRCs by immunohistochemistry. Among 168 MSI-H CRCs, nuclear staining for ANXA10 in tumor cells revealed 28 cases (17%) with ANXA10-positive (ANXA10+) tumors. Most of the ANXA10+ tumors were located in the proximal colon (96%, p < 0.001). The ANXA10+ phenotype in MSI-H CRC was significantly associated with female gender (68%, p = 0.016), CpG island methylator phenotype-high (CIMP-H) (68%, p < 0.001), MLH1 promoter hypermethylation (61%, p < 0.001), loss of MLH1 expression (82%, p = 0.019), and wild-type KRAS status (96%, p = 0.023). Survival analysis revealed no prognostic significance of ANXA10 expression in MSI-H CRC. In conclusion, ANXA10+ MSI-H colon carcinomas are characterized by serrated pathway features, including proximal location, female predominance, and high frequencies of CIMP-H status and MLH1 methylation.

Defined morphological criteria allow reliable diagnosis of colorectal serrated polyps and predict polyp genetics

Criteria for the diagnosis of serrated colorectal lesions (hyperplastic polyp, sessile serrated adenoma without or with dysplasia--which we called mixed polyp--and traditional serrated adenoma) for which consensus has been reached should be validated for applicability in daily practice in terms of inter-observer reproducibility and their association with clinical features and (epi)genetic events. A study set was created from a consecutive series of colorectal polyps (n = 1,926) by selecting all sessile serrated adenomas, traditional serrated adenomas and mixed polyps. We added consecutive series of hyperplastic polyps, classical adenomas and normal mucosa samples for a total of 200 specimens. With this series, we conducted an inter-observer study, encompassing ten pathologists with gastrointestinal pathology experience from five European countries, in three rounds in which all cases were microscopically evaluated. An assessment of single morphological criteria was included, and these were correlated with clinical parameters and the mutation status of KRAS, BRAF and PIK3CA and the methylation status of MLH1. Gender, age and localisation were significantly associated with certain types of lesions. Kappa statistics revealed moderate to good inter-observer agreement for polyp classification (κ = 0.56 to 0.63), but for single criteria, this varied considerably (κ = 0.06 to 0.82). BRAF mutations were frequently found in hyperplastic polyps (86 %, 62/72) and sessile serrated adenomas (80 %, 41/51). KRAS mutations occurred more frequently in traditional serrated adenomas (78 %, 7/9) and less so in classical adenomas (20 %, 10/51). Single morphological criteria for sessile serrated adenomas showed significant correlation with BRAF mutation (all p ≤ 0.001), and those for classical adenomas or traditional serrated adenoma correlated significantly with KRAS mutation (all p < 0.001). Therefore, single well-defined morphological criteria are predictive for genetic alterations in colorectal polyps.

Endoscopic versus histological characterisation of polyps during screening colonoscopy

BACKGROUND

As screening colonoscopy becomes more widespread, the costs for histopathological assessment of resected polyps are rising correspondingly. Reference centres have published highly accurate results for endoscopic polyp classification. Therefore, it has been proposed that, for smaller polyps, the differential diagnosis that guides follow-up recommendations could be based on endoscopy alone.

OBJECTIVE

The aim was to prospectively assess whether the high accuracy for endoscopic polyp diagnosis as reported by reference centres can be reproduced in routine screening colonoscopy.

DESIGN

Ten experienced private practice endoscopists had initial training in pit patterns. Then they assessed all polyps detected during 1069 screening colonoscopies. Patients (46% men; mean age 63 years) were randomly assigned to colonoscopy with conventional or latest generation HDTV instruments. The main outcome measure was diagnostic accuracy of in vivo polyp assessment (adenomatous vs hyperplastic). Secondary outcome measures were differences between endoscopes and reliability of image-based follow-up recommendations; a blinded post hoc analysis of polyp photographs was also performed.

RESULTS

675 polyps were assessed (461 adenomatous, 214 hyperplastic). Accuracy, sensitivity and specificity of in vivo diagnoses were 76.6%, 78.1% and 73.4%; size of adenomas and endoscope withdrawal time significantly influenced accuracy. Image-based recommendations for post-polypectomy surveillance were correct in only 69.5% of cases. Post hoc analysis of polyp photographs did not improve accuracy.

CONCLUSIONS

In everyday practice, endoscopic classification of polyp type is not accurate enough to abandon histopathological assessment and use of latest generation colonoscopes does not improve this. Image-based surveillance recommendations after polypectomy would consequently not meet guideline requirements.

TRIALREGNO

NCT01297712.

Interobserver agreement in the reporting of colorectal polyp pathology among bowel cancer screening pathologists in Wales

AIMS

To assess the interobserver agreement in the reporting of colorectal polyps among histopathologists participating in the Welsh Bowel Cancer Screening (BCS) programme.

METHODS AND RESULTS

Twelve benign polyps representative of BCS cases were identified from pathology files and reported by 28 BCS histopathologists using proforma sheets. The level of agreement between the participants and a gold standard was determined using kappa (κ) statistics. A moderate level of agreement was achieved in the reporting of polyp type [κ = 0.45; 95% confidence interval (CI) 0.34-0.59] and adenomatous lesions were distinguished from non-adenomatous lesions in 96% of cases. Substantial agreement was obtained in distinguishing low- and high-grade dysplasias (κ = 0.67; 95% CI 0.50-0.86), but there was only fair agreement in reporting excision margin status (κ = 0.24; 95% CI 0.07-0.43) with frequent use of the 'uncertain' category. Significant issues included categorizing serrated lesions, recognizing focal high-grade dysplasia and epithelial misplacement, and apparent overdiagnosis of villous change in adenomas.

CONCLUSIONS

Interobserver variability in some aspects of reporting colorectal polyps by BCS pathologists is suboptimal, with a potential impact upon patient management and the efficient running of the screening service. Approaches to addressing this are discussed.