Colorectal serrated pathway cancers and precursors

BRAF-mutant mismatch repair deficient invasive colon cancer regressing to sessile serrated lesion

A 69-year-old female was presented with a history of sigmoid colon cancer, uterine cancer, and intrahepatic carcinomas. After computed tomography revealed a disseminated nodule located in the peritoneum, colonoscopy demonstrated a rather flat-to-slightly elevated lesion with a depressed area located in the ascending colon. The flat component showed color similar to its surrounding area, and the depressed area showed redness and an expanded appearance. We obtained a biopsy specimen from the depressed area, and microscopic examination revealed well-differentiated adenocarcinoma, which was immunohistochemically positive for BRAF V600E-mutated and PMS2 proteins, and showed loss of MSH2 and MSH6 protein expressions. These findings suggested the lesion to have transformed from a sessile serrated lesion (SSL) to mismatch repair (MMR) deficient colon cancer. The patient underwent surgical removal of the nodule, which interpreted as metastasis of intrahepatic cholangiocarcinoma histopathologically. After postoperative chemotherapy, the follow-up colonoscopy revealed only the flat portion of the lesion without depressed area. Consequently, we performed an endoscopic resection, and microscopic examination confirmed the existence of BRAF V600E-mutated protein-positive and MMR protein-retained SSL without residual carcinoma. This is the first report of BRAF-mutant and MMR-deficient colon cancer, in association with SSL, showing regression.

Novel insights into tumorigenesis revealed by molecular analysis of Lynch syndrome cases with multiple colorectal tumors

Background

Lynch syndrome (LS) is an autosomal dominant multi-organ cancer syndrome with a high lifetime risk of cancer. The number of cumulative colorectal adenomas in LS does not generally exceed ten, and removal of adenomas via routine screening minimizes the cancer burden. However, abnormal phenotypes may mislead initial diagnosis and subsequently cause suboptimal treatment.

Aim

Currently, there is no standard guide for the care of multiple colorectal adenomas in LS individuals. We aimed to shed insight into the molecular features and reasons for multiplicity of adenomas in LS patients.

Methods

We applied whole exome sequencing on nine adenomas (ten samples) and three assumed primary carcinomas (five samples) of an LS patient developing the tumors during a 21-year follow-up period. We compared the findings to the tumor profiles of two additional LS cases ascertained through colorectal tumor multiplicity, as well as to ten adenomas and 15 carcinomas from 23 unrelated LS patients with no elevated adenoma burden from the same population. As LS associated cancers can arise via several molecular pathways, we also profiled the tumors for CpG Island Methylator Phenotype (CIMP), and LINE-1 methylation.

Results

All tumors were microsatellite unstable (MSI), and MSI was present in several samples derived from normal mucosa as well. Interestingly, frequent frameshift variants in RNF43 were shared among substantial number of the tumors of our primary case and the tumors of LS cases with multiple tumors but almost absent in our control LS cases. The RNF43 variants were completely absent in the normal tissue, indicating tumor-associated mutational hotspots. The RNF43 status correlated with the mutational signature SBS96. Contrary to LS tumors from the reference set with no elevated colorectal tumor burden, the somatic variants occurred significantly more frequently at C>T in the CpG context, irrespective of CIMP or LINE-1 status, potentially indicating other, yet unknown methylation-related mechanisms. There were no signs of somatic mosaicism affecting the MMR genes. Somatic variants in APC and CTNNB1 were unique to each tumor.

Conclusion

Frequent somatic RNF43 hot spot variants combined with SBS96 signature and increased tendency to DNA methylation may contribute to tumor multiplicity in LS.

Sessile serrated lesions with dysplasia: is it possible to nip them in the bud?

The serrated neoplasia pathway constitutes an "alternative route" to colorectal cancer (CRC), and sessile serrated lesions with dysplasia (SSLDs) are an intermediate step between sessile serrated lesions (SSLs) and invasive CRC in this pathway. While SSLs show indolent growth before becoming dysplastic (> 10-15 years), SSLDs are considered to rapidly progress to either immunogenic microsatellite instable-high (MSI-H) CRC (presumably 75% of cases) or mesenchymal microsatellite stable (MSS) CRC. Their flat shapes and the relatively short window of this intermediate state make it difficult to detect and diagnose SSLDs; thus, these lesions are potent precursors of post-colonoscopy/interval cancers. Confusing terminology and the lack of longitudinal observation data of serrated polyps have hampered the accumulation of knowledge about SSLDs; however, a growing body of evidence has started to clarify their characteristics and biology. Together with recent efforts to incorporate terminology, histological studies of SSLDs have identified distinct dysplastic patterns and revealed alterations in the tumor microenvironment (TME). Molecular studies at the single-cell level have identified distinct gene alterations in both the epithelium and the TME. Mouse serrated tumor models have demonstrated the importance of TME in disease progression. Advances in colonoscopy provide clues to distinguish pre-malignant from non-malignant-SSLs. Recent progress in all aspects of the field has enhanced our understanding of the biology of SSLDs. The aim of this review article was to assess the current knowledge of SSLDs and highlight their clinical implications.

Randomized Trial of Facilitated Adherence to Screening Colonoscopy vs Sequential Fecal-Based Blood Test

BACKGROUND & AIMS

Colorectal cancer (CRC) screening guidelines include screening colonoscopy and sequential high-sensitivity fecal occult blood testing (HSgFOBT), with expectation of similar effectiveness based on the assumption of similar high adherence. However, adherence to screening colonoscopy compared with sequential HSgFOBT has not been reported. In this randomized clinical trial, we assessed adherence and pathology findings for a single screening colonoscopy vs sequential and nonsequential HSgFOBTs.

METHODS

Participants aged 40-69 years were enrolled at 3 centers representing different clinical settings. Participants were randomized into a single screening colonoscopy arm vs sequential HSgFOBT arm composed of 4-7 rounds. Initial adherence to screening colonoscopy and sequential adherence to HSgFOBT, follow-up colonoscopy for positive HSgFOBT tests, crossover to colonoscopy, and detection of advanced neoplasia or large serrated lesions (ADN-SERs) were measured.

RESULTS

There were 3523 participants included in the trial; 1761 and 1762 participants were randomized to the screening colonoscopy and HSgFOBT arms, respectively. Adherence was 1473 (83.6%) for the screening colonoscopy arm vs 1288 (73.1%) for the HSgFOBT arm after 1 round (relative risk [RR], 1.14; 95% CI, 1.10-1.19; P ≤ .001), but only 674 (38.3%) over 4 sequential HSgFOBT rounds (RR, 2.19; 95% CI, 2.05-2.33). Overall adherence to any screening increased to 1558 (88.5%) in the screening colonoscopy arm during the entire study period and 1493 (84.7%) in the HSgFOBT arm (RR, 1.04; 95% CI, 1.02-1.07). Four hundred thirty-six participants (24.7%) crossed over to screening colonoscopy during the first 4 rounds. ADN-SERs were detected in 121 of the 1473 participants (8.2%) in the colonoscopy arm who were adherent to protocol in the first 12 months of the study, whereas detection of ADN-SERs among those who were not sequentially adherent (n = 709) to HSgFOBT was subpar (0.6%) (RR, 14.72; 95% CI, 5.46-39.67) compared with those who were sequentially adherent (3.3%) (n = 647) (RR, 2.52; 95% CI, 1.61-3.98) to HSgFOBT in the first 4 rounds. When including colonoscopies from HSgFOBT patients who were never positive yet crossed over (n = 1483), 5.5% of ADN-SERs were detected (RR, 1.50; 95% CI, 1.15-1.96) in the first 4 rounds.

CONCLUSIONS

Observed adherence to sequential rounds of HSgFOBT was suboptimal compared with a single screening colonoscopy. Detection of ADN-SERs was inferior when nonsequential HSgFOBT adherence was compared with sequential adherence. However, the greatest number of ADN-SERs was detected among those who crossed over to colonoscopy and opted to receive a colonoscopy. The effectiveness of an HSgFOBT screening program may be enhanced if crossover to screening colonoscopy is permitted.

CLINICALTRIALS

gov, Number: NCT00102011.

Three pathologic criteria for reproducible diagnosis of colonic sessile serrated lesion versus hyperplastic polyp

Colonic SSLs are thought to predispose to ∼30% of colonic adenocarcinomas. This increased risk, compared to benign HPs, makes their distinction vitally important. However, no gold standard exists to differentiate them, and wide observer variability is reported. To better distinguish these polyps, we investigated 94 serrated polyps (53 SSLs and 41 HPs) 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 8 expert gastrointestinal pathologists. By ROC analysis, polyp size by biopsy number performed best, followed by polyp location and morphology (areas under the curves [AUCs] = 85.9%, 81.2%, and 65.9%, respectively). Optimal discrimination combined all 3 features (AUC = 92.9%). For polyp size, the biopsy number proved superior to endoscopic size (AUC = 85.9% versus 55.2%, P = .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. The proposed 3-criteria pathologic system, combining size by biopsy number, location, and morphology, yields an improved, easy-to-use, and highly reproducible diagnostic approach for differentiating SSLs and HPs.

Body Mass Index, sex, non-steroidal anti-inflammatory drug medications, smoking and alcohol are differentially associated with World Health Organisation criteria and colorectal cancer risk in people with Serrated Polyposis Syndrome: an Australian case-control study

OBJECTIVE

The unknown aetiology of Serrated Polyposis Syndrome (SPS) impedes risk prediction and prevention. We investigated risk factors for SPS, overall and stratified by World Health Organization (WHO)²⁰¹⁰ clinical criteria and by colorectal cancer (CRC).

METHOD

A retrospective case-control study involving a cross-sectional analysis from 350 unrelated individuals with SPS from the Genetics of Colonic Polyposis Study and 714 controls from the Australasian Colorectal Cancer Family Registry. Univariate and multivariate logistic regression modelling was used to determine the association between risk factors and SPS and risk factors associated with CRC in SPS.

RESULTS

Female biological sex (odds ratio (OR) = 4.54; 95%Confidence interval (CI) = 2.77-7.45), increasing body mass index (BMI) at age 20 years (OR = 1.09; 95%CI = 1.04-1.13), hormone replacement therapy (OR = 0.44; 95%CI = 0.20.98), and increasing weekly folate intake (OR = 0.82; 95%CI = 0.75-0.90) were associated with SPS by multivariate analysis. Increasing weekly calcium intake (OR = 0.79; 95%CI = 0.64-0.97) and smoking > 10 cigarettes daily (OR = 0.45; 95%CI = 0.23-0.86) were associated with WHO criterion I only. The consumption of 1-100 g of alcohol per week (OR = 0.39; 95%CI = 0.18-0.83) was associated with WHO criterion III only. Smoking 1-5 cigarettes daily (OR = 2.35; 95%CI = 1.09-5.05), weekly non-steroidal anti-inflammatory drug (NSAIDs) intake (OR = 0.88; 95%CI = 0.78-0.99), and increased height (OR = 1.09; 95% = 1.05-1.13), were associated with SPS fulfilling both WHO criteria I and III. Moreover, weekly NSAIDs intake (OR = 0.81; 95%CI = 0.67-0.98) was associated with a reduced likelihood of CRC in SPS.

CONCLUSION

We identified novel risk and potential protective factors associated with SPS, some specific for certain WHO²⁰¹⁰ criteria. Weekly use of NSAIDs may reduce the risk of CRC in people with SPS.

Pure somatic pathogenic variation profiles for patients with serrated polyposis syndrome: a case series

OBJECTIVE

The serrated pathway is a distinct genetic/epigenetic mechanism of the adenoma-carcinoma sequence in colorectal carcinogenesis. Although many groups have reported the genetic-phenotypic correlation of serrated lesions (SLs), previous studies regarding the serrated pathway were conducted on patients with SLs that have different germline and environmental genetic backgrounds. We aimed to compare pure somatic genetic profiles among SLs within identical patient with SPS.

RESULTS

We analyzed SLs from one patient with SPS (Case #1) and compared DNA variant profiles using targeted DNA multigene panels via NGS among the patient's hyperplastic polyp (HP), three sessile serrated lesions (SSLs), and one traditional serrated adenoma (TSA), and separately analyzed three SSLs and one tubular adenoma (TA) within another patient with SPS (Case #2). In two patients, known pathogenic variant of BRAF (c.1799 T > A, p.Val600Glu) was observed in one TSA and one SSL in Case #1, and in three SSLs within Case #2. The pure somatic pathogenic variant BRAF (c.1799 T > A, p.Val600Glu) among SLs with identical germline genetic background supports its importance as a strong contributor for SLs.

Molecular and clinicopathological differences between depressed and protruded T2 colorectal cancer

Background

Colorectal cancer (CRC) can be classified into four consensus molecular subtypes (CMS) according to genomic aberrations and gene expression profiles. CMS is expected to be useful in predicting prognosis and selecting chemotherapy regimens. However, there are still no reports on the relationship between the morphology and CMS.

Methods

This retrospective study included 55 subjects with T2 CRC undergoing surgical resection, of whom 30 had the depressed type and 25 the protruded type. In the classification of the CMS, we first defined cases with deficient mismatch repair as CMS1. And then, CMS2/3 and CMS4 were classified using an online classifier developed by Trinh et al. The staining intensity of CDX2, HTR2B, FRMD6, ZEB1, and KER and the percentage contents of CDX2, FRMD6, and KER are input into the classifier to obtain automatic output classifying the specimen as CMS2/3 or CMS4.

Results

According to the results yielded by the online classifier, of the 30 depressed-type cases, 15 (50%) were classified as CMS2/3 and 15 (50%) as CMS4. Of the 25 protruded-type cases, 3 (12%) were classified as CMS1 and 22 (88%) as CMS2/3. All of the T2 CRCs classified as CMS4 were depressed CRCs. More malignant pathological findings such as lymphatic invasion were associated with the depressed rather than protruded T2 CRC cases.

Conclusions

Depressed-type T2 CRC had a significant association with CMS4, showing more malignant pathological findings such as lymphatic invasion than the protruded-type, which could explain the reported association between CMS4 CRC and poor prognosis.

Sessile serrated lesions in patients with adenoma on index colonoscopy do not increase metachronous advanced adenoma risk

OBJECTIVES

Post-polypectomy surveillance intervals should be determined based on index colonoscopy findings. However, the risk of metachronous lesions, resulting from the coexistence of adenoma and sessile serrated lesions (SSLs), has rarely been addressed. We evaluated the impact of synchronous SSL on the risk of metachronous lesions within similar adenoma risk groups.

METHODS

We retrieved individuals with one or more adenomas on index colonoscopy in a single-center retrospective cohort and stratified them into four groups depending on the presence of SSL and low-risk/high-risk adenoma (LRA/HRA). Participants who underwent surveillance colonoscopies at least 12 months apart were included. We compared the risks of metachronous lesions including HRA, advanced adenoma (AA), or SSL within similar adenoma risk groups according to the presence of SSL.

RESULTS

Overall 4493 individuals were included in the analysis. The risk of metachronous HRA/AA was not significantly higher in the adenoma with SSL group compared with the adenoma without SSL group, irrespective of LRA (HRA, 6/86 vs. 231/3297, P = 1.00; AA, 0/86 vs. 52/3297, P = 0.64) or HRA (HRA, 11/64 vs. 240/1046, P = 0.36; AA, 3/64 vs. 51/1046, P = 1.00). However, the risk of metachronous SSL in individuals with synchronous SSL was higher than that in those without SSL for both LRA (15/86 vs. 161/3297, P < 0.001) and HRA groups (11/64 vs. 61/1046, P = 0.002).

CONCLUSION

The presence of synchronous SSL did not increase the risk of metachronous HRA/AA, compared with isolated adenoma, but increased the risk of metachronous SSL.

Traditional Serrated Adenoma of the Gallbladder, a Case Report

While overwhelming majority of laparoscopic cholecystectomy specimens performed for gallstones or cholecystitis show rather typical findings, sometimes polypoid structures are also removed. These can be related to cholesterolosis or conventional adenomas, but occasionally extraordinary findings do emerge. In our case, a 67-year old lady with typical complaints of cholecystitis underwent routine laparoscopic cholecystectomy. Preoperative ultrasound revealed a polypoid mass with inflammation and without suspicion for malignancy. Microscopic examination showed partly conventional, low-grade dysplastic crypts forming a villous and rather complex structure. Ectopic crypt foci, slit-like serration pattern and serrated dysplasia with eosinophylic cytoplasm and centrally located nuclei were seen throughout the lesion, thus a traditional serrated adenoma (TSA) of the gallbladder was diagnosed. TSA represents the rarest subtype of serrated lesions in the colon and extracolonic manifestations are sporadically reported. Until now only a single case of a serrated adenoma was reported from the gallbladder. Here we describe the detailed clinical, pathological and molecular findings of our case and discuss these in the light of current literature data regarding this field.

Molecular pathways in post-colonoscopy versus detected colorectal cancers: results from a nested case-control study

BACKGROUND

Post-colonoscopy colorectal cancers (PCCRCs) pose challenges in clinical practice. PCCRCs occur due to a combination of procedural and biological causes. In a nested case-control study, we compared clinical and molecular features of PCCRCs and detected CRCs (DCRCs).

METHODS

Whole-genome chromosomal copy number changes and mutation status of genes commonly affected in CRC were examined by low-coverage WGS and targeted sequencing, respectively. MSI and CIMP status was also determined.

RESULTS

In total, 122 PCCRCs and 98 DCRCs with high-quality DNA were examined. PCCRCs were more often located proximally (P < 0.001), non-polypoid appearing (P = 0.004), early stage (P = 0.009) and poorly differentiated (P = 0.006). PCCRCs showed significantly less 18q loss (FDR < 0.2), compared to DCRCs. No significant differences in mutations were observed. PCCRCs were more commonly CIMP high (P = 0.014) and MSI (P = 0.029). After correction for tumour location, only less 18q loss remained significant (P = 0.005).

CONCLUSION

Molecular features associated with the sessile serrated lesions (SSLs) and non-polypoid colorectal neoplasms (CRNs) are more commonly seen in PCCRCs than in DCRCs. These together with the clinical features observed support the hypothesis that SSLs and non-polypoid CRNs are contributors to the development of PCCRCs. The future focus should be directed at improving the detection and endoscopic removal of these non-polypoid CRN and SSLs.

CLINICAL TRIAL REGISTRATION

NTR3093 in the Dutch trial register ( www.trialregister.nl ).

Sessile serrated adenoma/polyp detection rate of water exchange, Endocuff, and cap colonoscopy: A network meta-analysis

BACKGROUND AND AIM

Sessile serrated adenoma/polyp (SSA/P) may contribute to interval cancer. In a recent meta-analysis, water exchange (WE) was shown to be superior to Endocuff and cap colonoscopy at adenoma and advanced adenoma detection. The strong positive correlation between adenoma detection rate (ADR), advanced adenoma detection rate (AADR), and sessile serrated adenoma/polyp detection rate (SSA/PDR) prompted us to hypothesize that WE could significantly improve SSA/PDR compared with Endocuff and cap colonoscopy.

METHODS

The literature was searched for all randomized controlled trials (RCTs) that reported SSA/PDR as an outcome and included the keywords colonoscopy, and water exchange, Endocuff, or cap. We performed traditional network meta-analyses with random effect models comparing SSA/PDR of each method using air insufflation as the control and reported the odds ratios (ORs) with 95% confidence interval (CI). Performances were ranked based on P-score.

RESULTS

A total of 531 articles resulted from initial keywords search. Eleven RCTs were included in the analysis. A total of 7856 patients underwent air insufflation, WE, Endocuff, or cap colonoscopy. WE significantly increased SSA/PDR (OR 2.04; 95% CI 1.33-3.13). Endocuff (OR 1.15; 95% CI 0.94-1.41) and cap (OR 1.08; 95% CI 0.42-2.74) did not significantly impact SSA/P detection. P-scores for WE (0.96), Endocuff (0.49), cap (0.37), and air insufflation (0.17) suggested that WE had the highest SSA/PDR. The results did not change after adjusting for mean withdrawal time and indication for colonoscopy.

CONCLUSION

Water exchange significantly increases SSA/PDR and is superior to Endocuff and cap colonoscopy at detecting SSA/P.

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.

Screening and prevention of colorectal cancer

Mortality from colorectal cancer is reduced through screening and early detection; moreover, removal of neoplastic lesions can reduce cancer incidence. While understanding of the risk factors, pathogenesis, and precursor lesions of colorectal cancer has advanced, the cause of the recent increase in cancer among young adults is largely unknown. Multiple invasive, semi- and non-invasive screening modalities have emerged over the past decade. The current emphasis on quality of colonoscopy has improved the effectiveness of screening and prevention, and the role of new technologies in detection of neoplasia, such as artificial intelligence, is rapidly emerging. The overall screening rates in the US, however, are suboptimal, and few interventions have been shown to increase screening uptake. This review provides an overview of colorectal cancer, the current status of screening efforts, and the tools available to reduce mortality from colorectal cancer.

Differential diagnosis of appendiceal serrated lesions and polyps and low-grade appendiceal mucinous neoplasm: analysis of 88 cases

PURPOSE

To identify clinicopathological features for the differential diagnosis of appendiceal serrated lesions and polyps (SPs) and low-grade appendiceal mucinous neoplasm (LAMN) for the purpose of avoiding over-diagnosis.

METHODS

Clinical data and pathological features of 66 patients with SPs diagnosed at the Aerospace Center Hospital between January 2013 and January 2021 were collected and compared to 22 cases of LAMN.

RESULTS

SPs, compared with LAMN, are likely to be associated with acute inflammation (SPs 53.0% vs. LAMN 18.2%), and may be located in the appendix partly, although with smaller diameter (average 9.6 vs. 27.2 mm); epithelial structures of serrated (100% vs. 22.7%) and filiform villous (47.0% vs. 18.2%) were often found in SPs. SPs occasionally show attenuated or flattened morphology (16.7% vs. 100%) and undulating or scalloped (7.6% vs. 40.9%) structures, and can also be accompanied by diverticulum (18.2% vs. 18.2%) and acellular mucin in the appendiceal wall (16.7% vs. 54.5%), which causes confusion with LAMN. The key point of the differential diagnosis is to observe whether the muscularis mucosa exists (loss, 0% vs. 100%) and fibrosis of the appendiceal wall (0% vs. 100%). SMA immunohistochemistry can assist in the diagnosis. Calcification is also indicative of LAMN.

CONCLUSIONS

The epithelial structure of SPs can appear flattened and focally scalloped, and can be accompanied by mucin in the appendiceal wall, which may appear as complex lesions, easily over-diagnosed as LAMN. Key differential diagnostic features are identifying the structure of lamina propria, determining whether the muscularis mucosa exists, and whether the appendiceal wall is fibrotic.

Two intertwined compartments coexisting in sporadic conventional colon adenomas

Sporadic conventional colon adenomas are microscopically built of 2 intertwined compartments: one on top, harboring the dysplastic tissue that defines their histo-biomolecular attributes, and the other below, composed of non-dysplastic crypts with corrupted shapes (CCS). The CCS of 306 colon adenomas revealed asymmetric, haphazardly-distributed proliferating cell-domains (PC). In contrast, the PC-domains in normal controls were symmetric, being limited to the lower thirds of the crypts. In 28% out of 501 sporadic conventional adenomas, foci of p53-upregulated dysplastic tissue were found. The CCS in 30% of 108 sporadic adenomas showed p53-upregulated single cells, suggesting mounting somatic mutations. No p53-upregulated cells were found in the crypts of controls. In polypoid adenomas, the mucosa of the stalk without dysplastic tissue on top disclosed CCS with asymmetrical PC-domains and single p53-upregulated cells. The latter observations suggested that CCS had developed prior to and not after the growth of the dysplastic tissue on top. CCS were also found below colon adenomas in carcinogen-treated rats. It is concluded that the 2 intertwined histo-biological compartments of sporadic conventional colon adenomas are probably interdependent components. These findings may open new directions aimed to uncover the link between the normal colonic mucosa and the histogenesis of, conventional adenomas.

From Mixed Hyperplastic/Adenomatous Polyp to Sessile Serrated Lesion: A Long and Winding Road for Long and Winding Crypts

CONTEXT.—

During the past 3 decades, numerous articles in the literature have offered terminology, diagnostic criteria, and consensus recommendations regarding the entity currently referred to by the World Health Organization as sessile serrated lesion. Given the many names and various, variably reproducible diagnostic criteria ascribed to sessile serrated lesion, confusion persists for many pathologists and gastroenterologists regarding the diagnosis. This distinction is important, as sessile serrated lesion can progress to malignancy, unlike its main differential diagnosis, hyperplastic polyp. Research studies have shed light on the characteristic architecture and morphology, immunohistochemical patterns, and molecular alterations of sessile serrated lesion, and multiple consensus meetings around the globe have developed their criteria and nomenclature, often clashing or mixing terms.

OBJECTIVE.—

To provide a narrative review from the entity's early description to our current understanding.

DATA SOURCES.—

The existing scientific and clinical literature, published texts, medical society recommendations, and specialty consensus guidelines.

CONCLUSIONS.—

The current World Health Organization criteria are a distillation of this scientific process, but terminology is still a point of contention worldwide.

What could microRNA expression tell us more about colorectal serrated pathway carcinogenesis?

In the last two decades, the vision of a unique carcinogenesis model for colorectal carcinoma (CRC) has completely changed. In addition to the adenoma to carcinoma transition, colorectal carcinogenesis can also occur via the serrated pathway. Small non-coding RNA, known as microRNAs (miRNAs), were also shown to be involved in progression towards malignancy. Furthermore, increased expression of certain miRNAs in premalignant sessile serrated lesions (SSLs) was found, emphasizing their role in the serrated pathway progression towards colon cancer. Since miRNAs function as post-transcriptional gene regulators, they have enormous potential to be used as useful biomarkers for CRC and screening in patients with SSLs particularly. In this review, we have summarized the most relevant information about the specific role of miRNAs and their relevant signaling pathways among different serrated lesions and polyps as well as in serrated adenocarcinoma. Additional focus is put on the correlation between gut immunity and miRNA expression in the serrated pathway, which remains unstudied.

A Focused Review on Advances in Risk Stratification of Malignant Polyps

Colorectal cancer is the third most common cancer in both men and women in the United States, with most cases arising from precursor adenomatous polyps. Colorectal malignant polyps are defined as cancerous polyps that consist of tumor cells invading through the muscularis mucosae into the underlying submucosa (pT1 tumor). It has been reported that approximately 0.5-8.3% of colorectal polyps are malignant polyps, and the potential for lymph node metastasis in these polyps ranges from 8.5% to 16.1%. Due to their clinical significance, recognition of malignant polyps is critical for clinical teams to make treatment decisions and establish appropriate surveillance schedules after local excision of the polyps. There is a rapidly developing interest in malignant polyps within the literature as a result of an increasing number of identifiable adverse histologic features and recent advancements in endoscopic treatment techniques. The purpose of this paper is to have a focused review of the recent histopathologic literature of malignant polyps.

Molecular Biomarkers of Sessile Serrated Adenoma/Polyps

OBJECTIVES:

Sessile serrated adenoma/polyps (SSA/Ps) contribute up to 30% of all colon cancers. There is considerable histological overlap between SSA/Ps and hyperplastic polyps. Inadequate consensus exists among pathologists, and no molecular biomarkers exist to differentiate these lesions with high accuracy. Lack of reliable diagnosis adversely affects clinical care. We previously defined a novel 7-gene panel by RNA sequencing that differentiates SSA/Ps from hyperplastic polyps. Here, we use the 7-gene panel as a molecular approach to differentiate SSA/Ps and HPs with higher sensitivity and specificity in a large sample set from a tertiary health care center.

METHODS:

Reverse transcription quantitative polymerase chain reaction of the 7-gene panel was performed on 223 formalin-fixed, paraffin-embedded serrated polyp and normal colon samples. We compare the sensitivity and specificity of the 7-gene panel with the BRAF and KRAS mutation incidence in differentiating SSA/Ps and HPs. We also evaluate the clinical data of patients with SSA/Ps showing high and low expression of the gene panel.

RESULTS:

The 7-gene RNA expression panel differentiates SSA/Ps and HPs with 89.2% sensitivity and 88.4% specificity. The gene panel outperforms BRAF mutation in identification of SSA/Ps. Clinical data suggest that expression of the 7-gene panel correlates with the development of SSA/Ps in the future.

DISCUSSION:

This study describes a novel 7-gene panel that identifies SSA/Ps with improved accuracy. Our data show that RNA markers of SSA/Ps advance the distinction of serrated lesions and contribute to the study of the serrated pathway to colon cancer.

Evolving pathologic concepts of serrated lesions of the colorectum

Here, we provide an up-to-date review of the histopathology and molecular pathology of serrated colorectal lesions. First, we introduce the updated contents of the 2019 World Health Organization classification for serrated lesions. The sessile serrated lesion (SSL) is a new diagnostic terminology that replaces sessile serrated adenoma and sessile serrated polyp. The diagnostic criteria for SSL were revised to require only one unequivocal distorted serrated crypt, which is sufficient for diagnosis. Unclassified serrated adenomas have been included as a new category of serrated lesions. Second, we review ongoing issues concerning the morphology of serrated lesions. Minor morphologic variants with distinct molecular features were recently defined, including serrated tubulovillous adenoma, mucin-rich variant of traditional serrated adenoma (TSA), and superficially serrated adenoma. In addition to intestinal dysplasia and serrated dysplasia, minimal deviation dysplasia and not otherwise specified dysplasia were newly suggested as dysplasia subtypes of SSLs. Third, we summarize the molecular features of serrated lesions. The critical determinant of CpG island methylation development in SSLs is patient age. Interestingly, there may be ethnic differences in BRAF/KRAS mutation frequencies in SSLs. The molecular pathogenesis of TSAs is divided into KRAS and BRAF mutation pathways. SSLs with MLH1 methylation can progress into favorable prognostic microsatellite instability-positive (MSI+)/CpG island methylator phenotype-positive (CIMP+) carcinomas, whereas MLH1-unmethylated SSLs and BRAF-mutated TSAs can be precursors of poor-prognostic MSI−/CIMP+ carcinomas. Finally, based on our recent data, we propose an algorithm for stratifying risk subgroups of non-dysplastic SSLs.

Associations between molecular characteristics of colorectal serrated polyps and subsequent advanced colorectal neoplasia

PURPOSE

BRAF mutation and DNA hypermethylation have linked sessile serrated adenomas/polyps (SSA/Ps) to serrated colorectal cancer (CRC) in cross-sectional studies, but they have not been evaluated in a longitudinal study. We aimed to evaluate the associations between molecular markers of serrated polyps and subsequent advanced colorectal neoplasia.

METHODS

Study subjects included Kaiser Permanente Washington members aged 20-75 years who received an index colonoscopy between 1/1/1998 and 12/31/2007 and had hyperplastic polyps (HPs) or SSA/Ps according to study pathology review. Polyps from index colonoscopies were removed and assayed for BRAF mutation, CpG island methylator phenotype (CIMP), and MLH1 methylation. Pathology reports and biopsies from the subsequent lower gastrointestinal endoscopy through 1/1/2013 were reviewed for advanced colorectal neoplasia. We identified additional incident CRC cases through linkage to the Seattle-Puget Sound Surveillance Epidemiology and End Results registry. We used generalized estimating equations to calculate adjusted odds ratios (OR) and 95% confidence intervals (CI) for subsequent advanced colorectal neoplasia, comparing index serrated polyps with different molecular markers.

RESULTS

We included 553 individuals with index serrated polyps (420 HPs and 133 SSA/Ps) and 795 subsequent endoscopies. The prevalence of BRAF-mutant, CIMP-high, and MLH1-methylated serrated polyps were 51%, 4%, and 2%, respectively. BRAF and CIMP were not associated with subsequent advanced colorectal neoplasia. MLH1-methylated SSP/As were significantly more likely to have subsequent advanced neoplasia (OR = 4.66, 95% CI 1.06-20.51).

CONCLUSION

Our results suggest that BRAF-mutant and CIMP-high serrated polyps are not associated with subsequent advanced colorectal neoplasia. Among SSA/Ps, MLH1 methylation may be an important marker to identify high-risk CRC precursors.

Receptor tyrosine kinase fusions act as a significant alternative driver of the serrated pathway in colorectal cancer development

Serrated polyps are a clinically and molecularly heterogeneous group of lesions that can contribute to the development of colorectal cancers (CRCs). However, the molecular mechanism underlying the development of serrated lesions is still not well understood. Here, we combined multiple approaches to analyze the genetic alterations in 86 colorectal adenomas (including 35 sessile serrated lesions, 15 traditional adenomas, and 36 conventional adenomatous polyps). We also investigated the in vitro and in vivo oncogenic properties of a novel variant of the NCOA4-RET fusion gene. Molecular profiling revealed that sessile serrated lesions and traditional serrated adenomas have distinct clinicopathological and molecular features. Moreover, we identified receptor tyrosine kinase translocations exclusively in sessile serrated lesions (17%), and the observation was validated in a separate cohort of 34 sessile serrated lesions (15%). The kinase fusions as well as the BRAF and KRAS mutations were mutually exclusive to each other. Ectopic expression of a novel variant of the NCOA4-RET fusion gene promoted cell proliferation in vitro and in vivo, and the proliferation was significantly suppressed by RET kinase inhibitors. All of these underscored the importance of mitogen-activated protein kinase (MAPK) pathway activation in the serrated pathway of colorectal tumorigenesis. In addition, we demonstrated that the kinase fusion may occur early in the precursor lesion and subsequent loss of TP53 may drives the transformation to carcinoma during serrated tumorigenesis. In conclusion, we identified kinase fusions as a significant alternative driver of the serrated pathway in colorectal cancer development, and detecting their presence may serve as a biomarker for the diagnosis of sessile serrated lesions. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Colorectal sessile serrated lesion with large size or synchronous neoplasm: a prospective study

BACKGROUND

Colorectal sessile serrated lesion (SSL) with synchronous neoplasm or large size are linked to higher risk of cancer, but their characteristics are unclear.

METHODS

We prospectively included consecutive colorectal hyperplasic polyp and SSL collected at our institution from August 2011 to August 2012. The following data were collected and analyzed: age, gender, polyp site, aggregated polyp size, history of polyp, and synchronous neoplasm.

RESULTS

We collected 437 specimens including 353 (80.8%) hyperplasic polyp and 84 (19.2%) SSL. Compared with hyperplasic polyp, SSL was independently associated with proximal colon [odds ratio (OR) 3.61, P< 0.001], larger size (OR 3.98, P< 0.001), but not history of polyp, age or gender. Large SSL (≥1 vs <1 cm) was associated with polyp site (P= 0.035) and synchronous advanced adenoma and cancer (P< 0.001). SSL with synchronous adenoma and cancer were more likely found in males (OR 1.91, P= 0.001), elderly (OR 1.02, P= 0.033), and patients with the index polyp in proximal colon (OR 1.32, P= 0.022), but not related to history of adenoma and cancer. Moreover, synchronous adenoma, SSL and cancer were independently associated with male gender (OR 1.90, P< 0.001), but surprisingly not older age, histology of index polyp (SSL vs hyperplasic polyp), index-polyp site or history of adenoma and cancer.

CONCLUSIONS

This prospective study shows male gender is associated with both synchronous adenoma and cancer, and synchronous adenoma, SSL and cancer, while index polyp site is associated with synchronous adenoma and cancer.

Traditional serrated adenoma has two distinct genetic pathways for molecular tumorigenesis with potential neoplastic progression

BACKGROUND

Recent studies have shown that traditional serrated adenoma (TSA) can be classified into BRAF and KRAS subtypes. Here, we examined the clinicopathological and molecular findings of 73 TSAs.

MATERIALS AND METHODS

TSAs were subclassified into BRAF type (46 cases, type A) and KRAS type (27 cases, type B) and divided into polyp head (TSA component) and base (precursor component [PC]) to identify pathological and molecular differences between the two components. BRAF and KRAS mutations, microsatellite instability (MSI), and DNA methylation status of the TSA component and PC were analyzed. In addition, immunohistochemical expressions of annexin A10, MUC2, MUC5AC, MUC6, and CD10 were also examined. Finally, we compared endoscopic findings with histological features.

RESULTS

We classified type As into 31 type A1s with mutation of the corresponding PC (42.5%) and 15 type A2s without mutation of the PC (20.5%). None of the corresponding PCs without KRAS mutation were observed in type Bs. MSI was not detected in the TSAs examined. There were significant differences in the frequency of annexin A10 and MUC5AC expression between the three subtypes. Furthermore, we compared the TSA component with the corresponding PC to identify the progression mechanism between the two components. Methylation status played an important role in the progression of type A1 from the corresponding PC, unlike type A2 and type B. Finally, specific endoscopic findings were well correlated with distinct histological findings.

CONCLUSION

TSAs were heterogeneous tumors with two or three pathways to neoplastic progression.

Clinicopathological features, diagnosis, and treatment of sessile serrated adenoma/polyp with dysplasia/carcinoma

Sessile serrated adenoma/polyps (SSA/Ps) are early precursor lesions in the serrated neoplasia pathway, which results in BRAF-mutated colorectal carcinomas with not only high levels of microsatellite instability but also microsatellite stable. SSA/Ps with advanced histology, including cytological dysplasia or minimally invasive carcinomas, are important lesions because SSA/Ps are considered major contributors to "interval cancers" and these lesions can rapidly become dysplastic or invasive carcinomas. Clinicopathologically, SSA/Ps with dysplasia or invasive carcinoma were associated with advanced age, female sex, and proximal colon. Although SSA/Ps with submucosal invasive carcinoma were smaller and invaded less deeply into the submucosal layer than conventional tubular adenomas with submucosal invasive carcinoma, SSA/Ps with submucosal invasive carcinoma frequently had a mucinous component and exhibited a higher potential for lymphatic invasion and lymph node metastasis. In an SSA/P series, endoscopic characteristics, including (semi)pedunculated morphology, double elevation, central depression, and reddishness, may help accurately diagnose SSA/Ps with advanced histology. Removal of SSA/Ps with dysplasia or invasive carcinoma was recommended. Endoscopic treatment such as endoscopic mucosal resection or endoscopic submucosal dissection is useful for those lesions. However, surgical resection with lymph node dissection might be indicated when SSA/Ps with invasive carcinoma are endoscopically suspected, because these have the high risk of lymph node metastasis. Greater awareness may promote further research into improving the detection, recognition, and complete resection rates of SSA/Ps with dysplasia or invasive carcinoma and reduce the interval cancer rates.

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.

DNA methylation changes that precede onset of dysplasia in advanced sessile serrated adenomas

Background

Sessile serrated adenomas (SSAs) are common polyps which give rise to 20–30% of colorectal cancer (CRC). SSAs display clinicopathologic features which present challenges in surveillance, including overrepresentation in young patients, proclivity for the proximal colon and rarity of histologic dysplasia (referred to then as SSAs with dysplasia, SSADs). Once dysplasia develops, there is rapid progression to CRC, even at a small size. There is therefore a clinical need to separate the “advanced” SSAs at high risk of progression to SSAD and cancer from ordinary SSAs. Since SSAs are known to accumulate methylation over time prior to the development of dysplasia, SSAD backgrounds (the remnant SSA present within an SSAD) likely harbour additional methylation events compared with ordinary SSAs. We therefore performed MethyLight and comprehensive methylation array (Illumina MethylationEPIC) on 40 SSAD backgrounds and 40 matched ordinary SSAs, and compared the methylation results with CRC methylation, CRC expression and immunohistochemical data.

Results

SSAD backgrounds demonstrated significant hypermethylation of CpG islands compared with ordinary SSAs, and the proportion of hypermethylated probes decreased progressively in the shore, shelf and open sea regions. Hypomethylation occurred in concert with hypermethylation, which showed a reverse pattern, increasing progressively away from the island regions. These methylation changes were also identified in BRAF-mutant hypermethylated CRCs. When compared with CRC expression data, SV2B, MLH1/EPM2AIP1, C16orf62, RCOR3, BAIAP3, OGDHL, HDHD3 and ATP1B2 demonstrated both promoter hypermethylation and decreased expression. Although SSAD backgrounds were histologically indistinguishable from ordinary SSAs, MLH1 methylation was detectable via MethyLight in 62.9% of SSAD backgrounds, and focal immunohistochemical MLH1 loss was seen in 52.5% of SSAD backgrounds.

Conclusions

Significant hyper- and hypomethylation events occur during SSA progression well before the development of histologically identifiable changes. Methylation is a heterogeneous process within individual SSAs, as typified by MLH1, where both MLH1 methylation and focal immunohistochemical MLH1 loss can be seen in the absence of dysplasia. This heterogeneity is likely a generalised phenomenon and should be taken into account in future methylation-based studies and the development of clinical methylation panels.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0691-4) contains supplementary material, which is available to authorized users.

Colorectal Serrated Neoplasia: An Institutional 12-Year Review Highlights the Impact of a Screening Programme

Background

As the malignant potential of sessile serrated lesions/polyps (SSL/Ps) and traditional serrated adenomas (TSAs) has been clearly demonstrated, it is important that serrated polyps are identified and correctly classified histologically.

Aim

Our aim was to characterize the clinicopathological features of a series of SSL/Ps & TSAs, to assess the accuracy of the pathological diagnosis, the incidence, and the rate of dysplasia in SSL/Ps & TSAs.

Methods

We identified all colorectal serrated polyps between 01/01/2004 and 31/05/2016, by searching the laboratory information system for all cases assigned a “serrated adenoma” SNOMED code. All available and suitable slides were reviewed by one pathologist, who was blinded to the original diagnosis and the site of the polyp. Subsequently discordant cases, SSL/Ps with dysplasia, and all TSAs were reviewed by a second pathologist.

Results

Over a 149-month period, 759 “serrated adenoma” polyps were identified, with 664 (from 523 patients) available for review. 41.1% were reviewed by both pathologists; 15.1% (100/664) were reclassified, with the majority being changed from SSL/P to hyperplastic polyp (HYP) (66/664; 9.9%). 80.3% of these HYPs were located in the left colon, and the majority exhibited prolapse effect. There were 520 SSL/Ps (92.2%) & 40 TSAs (7.1%). The majority of SSL/Ps were in the right colon (86.7%) and were small (64.5% <1 cm), while most TSAs were in the left colon (85.7%) and were large (73.1%≥1 cm). 6.7% of SSL/Ps exhibited dysplasia, the majority of which were large (66.7%≥1 cm). Following consensus review, 13/520 (2.5%) SSL/Ps were downgraded from SSL/P with dysplasia to SSL/P without dysplasia. Detection of SSL/Ps peaked in the most recent years reviewed (87.5% reported between 2013 and 2016, inclusive), coinciding with the introduction of “BowelScreen” (the Irish FIT-based colorectal cancer screening programme).

Conclusions

Awareness of, and adherence to, diagnostic criteria is essential for accurate classification of colorectal polyps.

Molecular characterization of "sessile serrated" adenoma to carcinoma transition in six early colorectal cancers

Colorectal cancer (CRC) is a heterogeneous group of diseases both from the morphological and molecular point of view. The sessile serrated adenoma/polyp (SSA/P) has been proposed as the precursor lesion of CRCs characterized by CpG island methylator phenotype (CIMP), DNA mismatch repair (MMR) system deficiency, and BRAF gene mutations. However, no study so far investigated the molecular landscape of "sessile serrated" adenoma to carcinoma transition in early CRCs. Six formalin-fixed paraffin-embedded CRCs developed within SSA/P were profiled for the immunohistochemical expression of MMR proteins (MLH1, MSH2, MSH6, PMS2, and Ep-CAM), p16, and β-catenin. DNA was extracted from the two components of each sample, after microdissection, and characterized for CIMP status and by applying a custom hotspot multigene mutational profiling of 164 hotspot regions of eleven CRC-associated genes (AKT1, APC, BRAF, CTNNB1, KIT, KRAS, NRAS, PDGFRA, PIK3CA, PTEN, and TP53). Five out of the six CRCs shared the same molecular profile (i.e. CIMP positive, MSI status, and BRAF mutation) with their SSA/P components. One out of five CRCs was also APC mutated, whereas another one showed an additional TP53 mutation. The remaining case was CIMP negative and MMR proficient in both the components, harbored a BRAF mutation in the SSA/P counterpart, whereas the CRC one was APC and TP53 mutated and showed p16 and β-catenin dysregulation. This study provides the molecular evidence that SSA/P, even without cytological dysplasia, is a precursor lesion of CRC and that conventional CRC might arise from mixed polyp.

Preliminary Report: Multiple Clusters of Proliferating Cells in Non-dysplastic Corrupted Colonic Crypts Underneath Conventional Adenomas

BACKGROUND

The finding was recently reported of clusters of colonic crypts lined with indigenous normal epithelium displaying irregular shapes underneath the adenomatous glands of conventional (tubular or villous) adenomas. These abnormal crypts were named non-dysplastic corrupted colonic crypts (NDCs). This study explored the characteristics of cell proliferation in NDCs present in a cohort of conventional adenomas.

MATERIALS AND METHODS

Sections from six conventional adenomas were challenged with the proliferation marker Ki-67 (MIB1). MIB+ proliferating clusters were regarded as those exhibiting two or more adjoining MIB+ cells.

RESULTS

A total of 46 (range=1-18) NDCs were found underneath the six conventional adenomas. Out of the 46 NDCs, two exhibited only one proliferative cluster/crypt, 14 NDCs two clusters/crypt, 14 three clusters/crypt and the remaining 16 NDCs more than four distinct clusters/crypt.

CONCLUSION

This preliminary study showed, evidently for the first time, that multiple, apparently haphazardly distributed clusters of proliferating cells are present in NDCs. Since the Ki-67 proliferation marker only labels progenitor daughter cells generated by stem cells, each MIB+ cluster in each NDC must have been produced by a single stem cell. Consequently, individual NDCs may harbor several stem cells, a deduction that is in concert with recent studies showing that in the normal human colon, the number of stem cells per crypt is of the order of five to six, or about 5% of the cell population of a single crypt.

Molecular characterization of sessile serrated adenoma/polyps with dysplasia/carcinoma based on immunohistochemistry, next-generation sequencing, and microsatellite instability testing: a case series study

Background

Colorectal sessile serrated adenoma/polyps (SSA/Ps) are considered early precursor lesions in the serrated neoplasia pathway. Recent studies have shown associations of SSA/Ps with lost MLH1 expression, a CpG island methylator phenotype, and BRAF mutations. However, the molecular biological features of SSA/Ps with early neoplastic progression have not yet been fully elucidated, owing to the rarity of cases of SSA/P with advanced histology such as cytologic dysplasia or invasive carcinoma. In this study, we aimed to elucidate the molecular biological features of SSA/Ps with dysplasia/carcinoma, representing relatively early stages of the serrated neoplasia pathway.

Methods

We performed immunostaining for β-catenin, MLH1, and mucins (e.g., MUC2, MUC5AC, MUC6, and CD10); targeted next-generation sequencing; and microsatellite instability (MSI) testing in 8 SSA/P lesions comprised of 4 SSA/Ps with high-grade dysplasia and 4 SSA/Ps with submucosal carcinoma.

Results

Lost MLH1 expression was found in 5 cases. All lesions studied were positive for nuclear β-catenin expression. Regarding phenotypic mucin expression, all lesions were positive for MUC2, but negative for CD10. MUC5AC and MUC6 positivity was observed in 7 cases. Genetically, the most frequently mutated gene was BRAF (7 cases), and other mutations were detected in FBXW7 (3 cases); TP53 (2 cases), and KIT, PTEN, SMAD4, and SMARCB1 (1 case each). Furthermore, 4 of 8 lesions were MSI-high and the remaining 4 lesions were microsatellite-stable (MSS). Interestingly, all 4 MSI-high lesions displayed MLH1 loss, 3 of which harbored a FBXW7 mutation, but not a TP53 mutation. However, 2 MSS lesions harbored a TP53 mutation, although none harbored a FBXW7 mutation.

Conclusions

SSA/Ps with dysplasia/carcinoma frequently harbored BRAF mutations. Activation of the WNT/β-catenin signaling pathway may facilitate the development of dysplasia in SSA/Ps and progression to carcinoma. Furthermore, our results suggested that these lesions might be associated with both MSI-high and MSS colorectal cancer, which might be distinguished by distinct molecular biological features such as lost MLH1 expression, FBXW7 mutations, and TP53 mutations.

Small RNA sequencing of sessile serrated polyps identifies microRNA profile associated with colon cancer

Sessile serrated adenoma/polyps (SSA/Ps) of the colon account for 20-30% of all colon cancers. Small non-coding RNAs, including microRNAs (miRNAs), may function as oncogenes or tumor suppressor genes involved in cancer development. Small RNA sequencing (RNA-seq) was used to characterize miRNA profiles in SSA/Ps, hyperplastic polyps (HPs), adenomatous polyps and paired uninvolved colon. Our 108 small RNA-seq samples' results were compared to small RNA-seq data from 212 colon cancers from the Cancer Genome Atlas. Twenty-three and six miRNAs were differentially expressed in SSA/Ps compared to paired uninvolved colon and HPs, respectively. Differential expression of MIR31-5p, MIR135B-5p and MIR378A-5p was confirmed by RT-qPCR. SSA/P-specific miRNAs are similarly expressed in colon cancers containing genomic aberrations described in serrated cancers. Correlation of miRNA expression with consensus molecular subtypes suggests more than one subtype is associated with the serrated neoplasia pathway. Canonical pathway analysis suggests many of these miRNAs target growth factor signaling pathways.

The clinical significance and synchronous polyp burden of large (≥ 20 mm) sessile serrated polyps in patients without serrated polyposis syndrome

BACKGROUND

Sessile serrated polyps (SSPs) are important precursors of colorectal carcinoma and interval cancer. Large SSPs (≥ 20 mm) outside the definition of serrated polyposis syndrome (SPS) have not been studied in comparison with SPS. We aimed to describe the characteristics of patients with large SSPs in this context.

METHODS

Patients with at least one SSP (≥ 20 mm) were eligible. Data from three consecutive colonoscopies were used to compare clinical and endoscopic characteristics in three patient groups: SPS, a solitary large SSP, and patients with at least two SSPs without fulfilling the criteria for SPS (oligo-SSP). Data on the diagnostic colonoscopy were collected retrospectively, whereas the remaining data was collected prospectively.

RESULTS

67/146 patients (45.9 %) had SPS, 53/146 (36.3 %) had a solitary SSP, and 26/146 (17.8 %) were categorized as oligo-SSP. Personal (16.4 %, 9.4 %, and 11.5 %, respectively) and family (17.9 %, 17.0 %, and 23.1 %, respectively) history of colorectal carcinoma did not differ significantly between groups. Polyp burden was greater in SPS compared with solitary SSP but was not different from oligo-SSP (advanced adenomas: SPS 32.8 % vs. solitary SSP 9.4 % [P = 0.002] vs. oligo-SSP 34.6 % [P = 0.87]; ≥ 10 conventional adenomas: 11.9 % vs. 0 % [P = 0.01] vs. 3.8 % [P = 0.44], respectively). Dysplasia in large SSPs was frequent in all groups (41.1 % overall). SPS was recognized by referring endoscopists in only 9.0 % of cases.

CONCLUSION

Patients with oligo-SSPs have similar synchronous polyp burden and clinical characteristics as patients with SPS and may require similar surveillance. Modification of the criteria for the diagnosis of SPS to include this group seems warranted. Patients with a solitary SSP have a lower risk of synchronous polyps, including advanced adenomas. Larger studies are warranted to determine whether these patients may return to standard surveillance following complete examination and clearance of the colon.

A morphological and molecular study of proposed early forms of traditional serrated adenoma

AIMS

Traditional serrated adenoma (TSA) is the least common subtype of serrated colorectal polyp. Large protuberant lesions are easily recognised; however, the origins of TSAs are not known, and early forms have not been described. Some large TSAs present with a flat 'shoulder' component surrounding the central protuberant component. We hypothesised that small polyps with the same histology as these shoulder regions may represent early TSAs. Thus the primary aim of the study is to describe the histology of these presumptive early TSAs.

METHODS AND RESULTS

We collected 70 small (<10 mm) polyps that may represent early TSAs on the basis of typical TSA cytology covering the luminal surface. We also identified 12 large TSAs with a shoulder component resembling these small polyps. The study polyp patients had a mean age of 58 years, and 54% were female; the polyps had a mean diameter of 4.1 mm and were predominantly distal (71%). Morphologically, slit-like serrations were present in 81%, ectopic crypt formations were present in 67%, and a villous component was present in 47%. These histological features were similar to those of the 12 shoulder lesions. Immunohistochemical stains showed an absence of β-catenin nuclear expression in 96% of the small polyps, retained expression of MLH1 in 100%, and Ki67 positivity restricted to the crypt bases and ectopic crypt formations. BRAF and KRAS mutations were identified in 47% and 31% of the polyps, respectively. BRAF-mutated polyps were more likely than KRAS-mutated polyps to arise in a precursor polyp (82% versus 18%, P < 0.001), and were more likely to have slit-like serrations (100% versus 73%, P = 0.003).

CONCLUSIONS

These morphological, immunohistochemical and molecular findings are similar to what has been reported in large TSAs, and support the hypothesis that these polyps represent early forms of TSA.

The prognostic impact of CDX2 correlates with the underlying mismatch repair status and BRAF mutational status but not with distant metastasis in colorectal cancer

Loss of CDX2 expression has been proposed to be a prognostic biomarker in colorectal cancer (CRC) correlating with shorter overall (OS) and progression-free survival (PFS). Since metastatic disease, mismatch repair (MMR) deficiency, and the mutational status of BRAF are considered to be important prognostic determinants in CRC, the present study aimed to analyze CDX2 expression in correlation with these parameters. Immunohistochemistry for CDX2, hMLH1, and hMSH2 was applied to a study cohort of 503 CRC specimens (FIRE-3) and a matched case-control collection of 50 right-sided CRC specimens with synchronous distant metastases and 50 right-sided CRCs without distant metastases. Furthermore, the mutational status of BRAF gene was analyzed utilizing pyrosequencing. CDX2 expression significantly correlates with reduced OS (p = 0.008) within the study population. In both cohorts, a significant correlation of CDX2 expression and MMR deficiency as well as the presence of a BRAF mutation (each p > 0.001) was observed, whereas no correlation of CDX2 expression and synchronous metastasis could be obtained. In the case-control study, only patients with proficient MMR status showed a correlation of CDX2 loss and synchronous metastasis, whereas in patients with deficient MMR status and CDX2 loss, no distant metastases at the time of diagnosis were found (p = 0.003). We could demonstrate that the reduced OS of CDX2-negative CRC patients is not caused by higher rates of distant metastases. Furthermore, our data indicate that the prognostic impact of CDX2 depends on the MMR status and the BRAF mutational status of the tumors. Thus, it could be concluded that CDX2 is not an independent prognostic biomarker in CRC.

Strategy to targeting the immune resistance and novel therapy in colorectal cancer

Assessing the CRC subtypes that can predict the outcome of colorectal cancer (CRC) in patients with immunogenicity seems to be a promising strategy to develop new drugs that target the antitumoral immune response. In particular, the disinhibition of the antitumoral T‐cell response by immune checkpoint blockade has shown remarkable therapeutic promise for patients with mismatch repair (MMR) deficient CRC. In this review, the authors provide the update of the molecular features and immunogenicity of CRC, discuss the role of possible predictive biomarkers, illustrate the modern immunotherapeutic approaches, and introduce the most relevant ongoing preclinical study and clinical trials such as the use of the combination therapy with immunotherapy. Furthermore, this work is further to understand the complex interactions between the immune surveillance and develop resistance in tumor cells. As expected, if the promise of these developments is fulfilled, it could develop the effective therapeutic strategies and novel combinations to overcome immune resistance and enhance effector responses, which guide clinicians toward a more “personalized” treatment for advanced CRC patients.

Clinicopathological features of advanced colorectal serrated lesions: A single-center study in China

OBJECTIVE

A growing body of evidence indicates that patients with colorectal serrated lesions, especially advanced serrated lesions (ASLs), are at risk of subsequent malignancy. This study aimed to analyze the clinicopathological features of ASLs and the association between ASLs and synchronous advanced colorectal neoplasia (sACN) in a single center of China.

METHODS

A retrospective cross-sectional study of consecutive symptomatic patients and healthy individuals who underwent colonoscopy between January 2010 and March 2016 was performed. Clinicopathological characteritics of the patients with ASLs were documented from the colonoscopy database.

RESULTS

Colorectal serrated lesions were pathologically confirmed in 277 (N = 38 981, 0.7%) cases. Among them, 156 (56.3%) were found to have ASLs, with a total of 161 lesions including 71 sessile serrated adenoma/polyps (SSA/P) and 90 traditional serrated adenomas (TSAs). There were no differences in age and gender between the ASL and non-ASL patients. Among the 161 ASLs, 29 (18.0%) were ≥10 mm in diameter. Compared with non-ASLs, ASLs appeared more in the proximal colon (P = 0.007). Flat and subpedunculated lesions were more commonly found in the ASL group compared with the non-ASL group. Nearly all ASLs (160/161) had dysplasia. Moreover, 16 sACN lesions were found in 156 ASL patients, and large diameter (≥10 mm) might be a significant risk factor for sACN (odds ratio 4.35, 95% confidence interval 1.467-12.894, P < 0.05).

CONCLUSIONS

ASLs are more likely to occur in the proximal colon, and mainly present as flat and sub-pedunculated types. Large ASLs are significantly associated with sACN.

Serrated adenocarcinoma morphology in colorectal mucinous adenocarcinoma is associated with improved patient survival

Colorectal mucinous adenocarcinoma (MAC) and serrated adenocarcinoma (SAC) share many characteristics, including right-side colon location, frequent mucin production, and various molecular features. This study examined the frequency of SAC morphology in MACs. We assessed the correlation of SAC morphology with clinicopathological parameters, molecular characteristics, and patient prognosis. Eighty-eight colorectal MACs were collected and reviewed for SAC morphology according to Makinen's criteria. We sequenced KRAS and BRAF, assessed CpG island methylator phenotype (CIMP) frequency, and analyzed DNA mismatch repair enzyme levels using immunohistochemistry in tumor samples. SAC morphology was observed in 38% of MACs, and was associated with proximal location (P=0.001), BRAF mutation (P=0.042), CIMP-positive status (P=0.023), and contiguous traditional serrated adenoma (P=0.019). Multivariate analysis revealed that MACs without both SAC morphology and CIMP-positive status exhibited 3.955 times greater risk of cancer relapse than MACs having both characteristics or either one (P=0.035). Our results show that two MAC groups with distinct features can be identified using Makinen's criteria, and suggest a favorable prognostic role for the serrated neoplastic pathway in colorectal MAC.

The role of APC in WNT pathway activation in serrated neoplasia

Conventional adenomas are initiated by APC gene mutation that activates the WNT signal. Serrated neoplasia is commonly initiated by BRAF or KRAS mutation. WNT pathway activation may also occur, however, to what extent this is owing to APC mutation is unknown. We examined aberrant nuclear β-catenin immunolocalization as a surrogate for WNT pathway activation and analyzed the entire APC gene coding sequence in serrated and conventional pathway polyps and cancers. WNT pathway activation was a common event in conventional pathway lesions with aberrant nuclear immunolocalization of β-catenin and truncating APC mutations in 90% and 89% of conventional adenomas and 82% and 70% of BRAF wild-type cancers, respectively. WNT pathway activation was seen to a lesser extent in serrated pathway lesions. It occurred at the transition to dysplasia in serrated polyps with a significant increase in nuclear β-catenin labeling from sessile serrated adenomas (10%) to sessile serrated adenomas with dysplasia (55%) and traditional serrated adenomas (9%) to traditional serrated adenomas with dysplasia (39%) (P=0.0001). However, unlike the conventional pathway, truncating APC mutations were rare in the serrated pathway lesions especially sessile serrated adenomas even when dysplastic (15%) and in the BRAF mutant cancers with microsatellite instability that arise from them (8%). In contrast, APC missense mutations that were rare in conventional pathway adenomas and cancers (3% in BRAF wild-type cancers) were more frequent in BRAF mutant cancers with microsatellite instability (32%). We conclude that increased WNT signaling is important in the transition to malignancy in the serrated pathway but that APC mutation is less common and the spectrum of mutations is different than in conventional colorectal carcinogenesis. Moderate impact APC mutations and non-APC-related causes of increased WNT signaling may have a more important role in serrated neoplasia than the truncating APC mutations common in conventional adenomas.

Tumour spheres with inverted polarity drive the formation of peritoneal metastases in patients with hypermethylated colorectal carcinomas

Metastases account for 90% of cancer-related deaths; thus, it is vital to understand the biology of tumour dissemination. Here, we collected and monitored >50 patient specimens ex vivo to investigate the cell biology of colorectal cancer (CRC) metastatic spread to the peritoneum. This reveals an unpredicted mode of dissemination. Large clusters of cancer epithelial cells displaying a robust outward apical pole, which we termed tumour spheres with inverted polarity (TSIPs), were observed throughout the process of dissemination. TSIPs form and propagate through the collective apical budding of hypermethylated CRCs downstream of canonical and non-canonical transforming growth factor-β signalling. TSIPs maintain their apical-out topology and use actomyosin contractility to collectively invade three-dimensional extracellular matrices. TSIPs invade paired patient peritoneum explants, initiate metastases in mice xenograft models and correlate with adverse patient prognosis. Thus, despite their epithelial architecture and inverted topology TSIPs seem to drive the metastatic spread of hypermethylated CRCs.

Sessile serrated adenomas with dysplasia: morphological patterns and correlations with MLH1 immunohistochemistry

Sessile serrated adenomas are the precursor polyp of approximately 20% of colorectal carcinomas. Sessile serrated adenomas with dysplasia are rarely encountered and represent an intermediate step to malignant progression, frequently associated with loss of MLH1 expression. Accurate diagnosis of these lesions is important to facilitate appropriate surveillance, particularly because progression from dysplasia to carcinoma can be rapid. The current World Health Organization classification describes two main patterns of dysplasia occurring in sessile serrated adenomas, namely, serrated and conventional. However, this may not adequately reflect the spectrum of changes seen by pathologists in routine practice. Furthermore, subtle patterns of dysplasia that are nevertheless associated with loss of MLH1 expression are not encompassed in this classification. We performed a morphological analysis of 266 sessile serrated adenomas with dysplasia with concurrent MLH1 immunohistochemistry with the aims of better defining the spectrum of dysplasia occurring in these lesions and correlating dysplasia patterns with MLH1 expression. We found that dysplasia can be divided morphologically into four major patterns, comprising minimal deviation (19%), serrated (12%), adenomatous (8%) and not otherwise specified (79%) groups. Minimal deviation dysplasia is defined by minor architectural and cytological changes that typically requires loss of MLH1 immunohistochemical expression to support the diagnosis. Serrated dysplasia and adenomatous dysplasia have distinctive histological features and are less frequently associated with loss of MLH1 expression (13 and 5%, respectively). Finally, dysplasia not otherwise specified encompasses most cases and shows a diverse range of morphological changes that do not fall into the other subgroups and are frequently associated with loss of MLH1 expression (83%). This morphological classification of sessile serrated adenomas with dysplasia may represent an improvement on the current description as it correlates with the underlying mismatch repair protein status of the polyps and better highlights the range of morphologies seen by pathologists.

WNT Pathway Gene Mutations Are Associated With the Presence of Dysplasia in Colorectal Sessile Serrated Adenoma/Polyps

Sessile serrated adenoma/polyps (SSA/Ps) are believed to be the major precursor of serrated pathway-derived colorectal carcinomas. To better characterize the process of progression from SSA/Ps to carcinomas, we analyzed 46 SSA/Ps with dysplasia and 45 SSA/Ps without dysplasia using targeted next-generation sequencing and immunohistochemistry. Among the WNT pathway genes analyzed, protein-truncating mutations of RNF43, APC, and ZNRF3 were identified in 23 (50%), 4 (9%), and 3 (7%) SSA/Ps with dysplasia, respectively. In contrast, SSA/Ps without dysplasia rarely had WNT pathway gene mutations, except for 3 lesions with RNF43 mutations (7%). None of the SSA/Ps had CTNNB1 mutations or RSPO fusions. Thus, WNT pathway gene mutations were more common in SSA/Ps with dysplasia than in SSA/Ps without dysplasia (P=3.0×10). Consistently, nuclear β-catenin accumulation and MYC overexpression, indicative of active WNT signaling, were present in most of the SSA/Ps with dysplasia, but were rare in those without dysplasia. BRAF (86%) or KRAS mutations (7%) were identified in the majority of SSA/Ps, regardless of the presence or absence of dysplasia. MLH1 expression was lost in 14 SSA/Ps with dysplasia (30%). The majority of MLH1-deficient SSA/Ps with dysplasia had RNF43 mutations (86%), most of which were frameshift mutations involving mononucleotide repeats. In contrast, MLH1-retained lesions had less frequent RNF43 mutations with no hot spots (34%), and 4 had APC mutations (13%). These results suggest that WNT pathway gene mutations are involved in the development of dysplasia in SSA/Ps and that MLH1-deficient and MLH1-retained SSA/Ps with dysplasia exhibit distinct mutation profiles of WNT pathway genes.

What influences preneoplastic colorectal lesion recurrence?

The hypothesis of the local recurrence of preneoplastic lesions was first put forward in the 1950s. Disease recurrence may result from an inherent imbalance in cell proliferation that promotes carcinogenesis in apparently normal mucosa. Our review sheds light on how early preneoplastic lesions could be used to diagnose relapsed preneoplastic and, developing neoplastic lesions. We focus in detail on the clinical-pathological and molecular features of adenoma subtypes and their role in relapsed adenoma and their development into colorectal carcinoma. Moreover, we include the data available on microbiota and its metabolites and their role in recurrence. We strongly believe that a significant improvement could be achieved in colorectal screening by introducing personalized endoscopic surveillance for polyp-bearing patients on the basis of the presence of molecular markers that are predictive of recurrence.

The third pathway of colorectal carcinogenesis

Aims

The majority of the colorectal carcinomas (CRC) arise in a vast mucosal area built with columnar cells and mucus-producing goblet cells. These carcinomas evolve via the conventional (tubular/villous) adenoma–carcinoma pathway, or the serrated adenoma–carcinoma pathway. Much less frequently CRC arise in the gut-associated lymphoid tissue (GALT) mucosal domain via the third pathway of colorectal carcinogenesis.

Methods

All publications on human colorectal GALT carcinomas in the literature were reviewed.

Results

Only 23 GALT-carcinomas found in 20 patients are in record. The GALT carcinomas were detected at surveillance colonoscopic biopsy in 11 patients (four had ulcerative colitis, two were members of a Lynch syndrome family, two of a CRC family, one had familial adenomatous polyposis (FAP), one prior colon adenomas and one a submucosal tumour), or at diagnostic colonoscopic biopsy in the remaining nine patients (three had rectal bleedings, two abdominal pains, one diverticular disease and one protracted constipation. In three, no ground disease or symptoms were provided). In six of the 23 GALT carcinomas, the luminal surface showed tumour cells, ulcerations or no descriptions were given. Ten (66.7%) of the remaining 15 GALT carcinomas showed on top, adenomas (n=8) or high-grade dysplasia (n=2).

Conclusions

The low frequency of GALT carcinomas might be explained by the fact that the colorectal mucosal areas occupied by GALT domains are minute. The finding that two-thirds of the 15 remaining GALT carcinomas (vide supra) were covered by high-grade dysplasia or by conventional adenomas strongly suggest that conventional non-invasive neoplasias might have preceded the majority of the GALT carcinomas in record.

Serrated lesions and serrated polyposis syndrome

The serrated pathway has been shown to be an alternative colorectal carcinogenetic route potentially accounting for up to one third of all CRCs. Serrated lesions, particularly SSPs, have been a focus of research during the past few years. They have well-established histological and molecular characteristics that account for their potential carcinogenetic risk through the accumulation BRAF, KRAS and methylator profile (CpG) mutations. Their endoscopic identification and resection represent a challenge because of their specific characteristics, and the need for an adequate specimen for histological diagnosis. Knowledge of these lesions is key, as is the adoption of established criteria for their endoscopic description and histological diagnosis. SPS is the maximum expression of involvement by serrated lesions, is associated with increased risk for CRC, and requires attentive endoscopic follow-up, as well as family screening. While the exact etiopathogenic mechanism remains unknown, current research will likely provide us with appropriate answers in the not too distant future.

GNAS mutations are present in colorectal traditional serrated adenomas, serrated tubulovillous adenomas and serrated adenocarcinomas with adverse prognostic features

AIMS

Activating mutations in GNAS are important in the development of a range of neoplasms, including a small proportion of conventional adenomas and colorectal carcinomas (CRCs). However, their contribution to serrated pathway neoplasia is unclear, as mutations have only been examined in small series of sessile serrated adenomas (SSAs) and traditional serrated adenomas (TSAs), and not in serrated tubulovillous adenomas (sTVAs). The aim of this study was to investigate the frequency and significance of GNAS mutations in colorectal adenomas and CRCs.

METHODS AND RESULTS

Using a large, well-characterized series, we identified GNAS mutations in 9.2% (18 of 196) of TSAs, 7.1% (four of 56) of sTVAs and 2.0% (nine of 459) of CRCs. Mutations were absent in SSAs (none of 43), tubular adenomas (none of 50) and conventional tubulovillous adenomas (none of 50). A BRAF or KRAS mutation was seen in 77.4% of GNAS mutant lesions, suggesting a synergistic effect with the mitogen-activated protein kinase pathway. In CRCs, GNAS mutations were associated with mucinous differentiation and serrated morphological features.

CONCLUSIONS

GNAS mutations contribute significantly to the development of a subset of serrated adenomas and CRCs.