Hyperplastic and serrated polyps of the colorectum

Multiple Protein Biomarkers and Different Treatment Strategies for Colorectal Carcinoma: A Comprehensive Prospective

In this review, we emphasized important biomarkers, pathogenesis, and newly developed therapeutic approaches in the treatment of colorectal cancer (CRC). This includes a complete description of small-molecule inhibitors, phytopharmaceuticals with antiproliferative potential, monoclonal antibodies for targeted therapy, vaccinations as immunotherapeutic agents, and many innovative strategies to intervene in the interaction of oncogenic proteins. Many factors combine to determine the clinical behavior of colorectal cancer and it is still difficult to comprehend the molecular causes of a person's vulnerability to CRC. It is also challenging to identify the causes of the tumor's onset, progression, and responsiveness or resistance to antitumor treatment. Current recommendations for targeted medications are being updated by guidelines throughout the world in light of the growing number of high-quality clinical studies. So, being concerned about the aforementioned aspects, we have tried to present a summarized pathogenic view, including a brief description of biomarkers and an update of compounds with their underlying mechanisms that are currently under various stages of clinical testing. This will help to identify gaps or shortfalls that can be addressed in upcoming colorectal cancer research.

The Impact of BRAF Mutation Status on Survival Outcomes and Treatment Patterns among Metastatic Colorectal Cancer Patients in Alberta, Canada

Colorectal cancer presents via multiple different clinical phenotypes that can arise from a variety of different genetic and molecular alterations. The aim of this study was to describe survival outcomes and treatment patterns of metastatic colorectal cancer (mCRC) patients by v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutation status. The Alberta Cancer Registry was used to identify all patients >18 years old who had been diagnosed with mCRC in Alberta between 1 January 2017 and 31 December 2019 and had received at least one cycle of systemic therapy. Treatment patterns were compared between wild-type and mutant BRAF mCRC patients. Cox regression models and Kaplan-Meier curves were created to assess survival differences by both treatment pattern and BRAF status. A total of 488 patients were identified with mCRC, of which 42 (11.4%) were confirmed to have a BRAF mutation. The most common first-line treatment regimen was either capecitabine and oxaliplatin (CAPOX) or leucovorin calcium (folinic acid), fluorouracil, and oxaliplatin (FOLFOX). The median overall survival for mCRC patients was 20.01 months. Mutant BRAF patients had a median survival of 8.21 months compared to 20.03 months among those with wild-type BRAF. BRAF mutations among mCRC patients are associated with a considerably poor prognosis, reinforcing the need for clinical BRAF testing among newly diagnosed patients to better understand their prognosis.

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.

Association of 25(OH)-Vitamin D and metabolic factors with colorectal polyps

BACKGROUND

Studies have revealed the association of vitamin D with specific types of cancer development, however, its correlation with colorectal polyps (CRPs) remains unverified. Our study aimed to investigate the relationship between vitamin D levels, metabolic factors, and CRPs.

METHODS

A cross-sectional study from 2017 to 2019 involving 1306 participants was conducted to investigate the association among vitamin D levels, metabolic factors, uric acid and CRPs in Taiwan. CRPs diagnoses were determined via colonoscopies conducted by experienced gastrointestinal physicians, and biopsied polyps were inspected under a microscope by experienced pathologists. We employed both simple and multiple logistic regression analyses to identify significant factors associated with CRPs and adenomatous polyps, respectively.

RESULTS

Our result showed that the prevalence of 25(OH)-vitamin D deficiency (≦ 20 ng/mL) and CRPs was 21.21% and 40.89%, respectively. Multiple logistic regression revealed that the risk of CRPs increased with old age, male sex, hyperglycemia, high triglyceride levels, and low 25(OH)D levels after adjustment for other factors. Besides, low 25(OH)D levels were significantly associated with CRPs risk in women, whereas elevated blood pressure was associated with CRPs risk in men. 25(OH)D Deficiency was revealed to be significantly associated with risk of CRPs in adults over 50 years old. Compared to nonadenomatous polyps, older age, higher 25(OH) vitamin D and higher uric acid levels were at increased risk for adenomatous polyps.

CONCLUSIONS

Our study revealed that vitamin D deficiency was significantly associated with the risk of CRPs, especially in adults over 50 years old and women. We should therefore be concerned about the CRP risk of vitamin D deficiency and metabolic syndrome (especially hyperglycemia, elevated blood pressure in men, and high triglyceride levels) in this population.

BRAF Mutations in Colorectal Liver Metastases: Prognostic Implications and Potential Therapeutic Strategies

Simple Summary

In this literature review, we investigated the relationship between BRAF mutation and prognosis in patients with colorectal cancer liver metastases. We also investigated factors affecting the prognosis of patients with BRAF mutations and summarized the latest research on targeted therapies.

Abstract

Surgery combined with chemotherapy and precision medicine is the only potential treatment for patients with colorectal cancer liver metastases (CRLM). The use of modern molecular biotechnology to identify suitable biomarkers is of great significance for predicting prognosis and formulating individualized treatment plans for these patients. BRAF mutations, particularly V600E, are widely believed to be associated with poor prognosis in patients with metastatic CRC (mCRC). However, it is unclear which specific factors affect the prognosis of CRLM patients with BRAF mutations. It is also unknown whether patients with resectable CRLM and BRAF mutations should undergo surgical treatment since there is an increased recurrence rate after surgery in these patients. In this review, we combined the molecular mechanism and clinical characteristics of BRAF mutations to explore the prognostic significance and potential targeted therapy strategies for patients with BRAF-mutated CRLM.

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.

Expression of Parkin, APC, APE1, and Bcl-xL in Colorectal Polyps

Colorectal cancer can develop through molecular, chromosomal, and epigenetic cumulative changes that transform the normal intestinal epithelium into the colorectal polyps, called conventional adenomas (CAs) or serrated polyps (SPs), recognized as precursors of invasive colorectal neoplasia. These benign lesions need to explore the morphology, histological diagnosis, and biomarkers profile to accurately characterize lesions with potential for evolution to cancer. This study aimed to correlate the immunohistochemical expression of Parkin and Adenomatous Polyposis Coli (APC; tumor suppressors), Human Apurinic/Apyrimidinic endonuclease 1 (APE1), and B-cell lymphoma-extra-large (Bcl-xL; oncogenic proteins) in sporadic colorectal polyps with clinical, endoscopic, and diagnostic data. Immunohistochemical analysis was performed on tissue microarray samples of 306 polyps. Based on the Allred score, the expressions were graduated in the cytoplasm and nucleus of superficial and cryptic cells. There was higher Parkin nuclear expression (p=0.006 and 0.010) and APC cytoplasmic expression in cryptic cells (p<0.001) in SPs. CAs, APE1 (p<0.001) and Bcl-xL (p<0.001) were more expressed in the nuclei and cytoplasms, respectively. These results are related to the biological role proposed for these proteins in cellular functions. They can contribute to the diagnosis criteria for polyps and improve the knowledge of biomarkers that could predict cancer development.

Interobserver variability in histological diagnosis of serrated colorectal polyps

Objectives To compare the interobserver variability in the diagnostic of serrated and non-serrated adenomatous lesions and hyperplastic polyps of colon between two groups of pathologists.

Methods 310 colorectal polyps were studied, with histological diagnoses established by a group of pathologists comprising three general pathologists for initial diagnosis, and two gastrointestinal pathologists for expert diagnosis.

Results High interobserver variability was observed in the diagnosis of serrated polyps, when comparing the initial diagnosis with the expert diagnosis (kappa = 0.102). For the majority of both traditional serrated adenomas and sessile serrated adenomas (27/31), a diagnosis of hyperplastic polyps was established at the initial diagnosis.

Conclusions Poor agreement was observed in the diagnosis of serrated polyps between the two groups of pathologists. The accuracy in the diagnosis of these lesions is essential for the prevention of colorectal cancer.

Agrin in the Muscularis Mucosa Serves as a Biomarker Distinguishing Hyperplastic Polyps from Sessile Serrated Lesions

PURPOSE

Sessile serrated lesions (SSL) are precursors to colon carcinoma, and their distinction from other polyps, in particular hyperplastic polyps (HP), presents significant diagnostic challenges. We evaluated expression patterns in colonic polyps of previously identified colon carcinoma-associated extracellular matrix (ECM) proteins to identify markers distinguishing SSLs from other polyps.

EXPERIMENTAL DESIGN

Gene-expression analyses of ECM proteins were performed using publicly available data on preneoplastic colonic polyps. In parallel, we evaluated by IHC the expression of agrin (AGRN) in over 400 colonic polyps, including HP, SSL with and without dysplasia, traditional serrated adenomas (TSA), and tubular adenomas (TA), and compared the consistency of standard histologic diagnosis of SSLs by experienced gastrointestinal pathologists with that of AGRN IHC.

RESULTS

Differential gene expression analysis and IHC identified AGRN, serine peptidase inhibitor (SERPINE2), and TIMP metallopeptidase inhibitor 1 (TIMP1) elevated in SSLs and HPs but decreased in TAs and absent in normal colon. AGRN-positive basal laminae were noted in all TA, TSA, HP, and SSL in distinguishable patterns, whereas other polyps and normal mucosa were negative. SSL with or without dysplasia consistently showed IHC staining for AGRN in the muscularis mucosae, which was absent in HP, TSA, TA, and other polyps. In contrast, histologic evaluation showed only weak interobserver agreement (kappa value = 0.493) in distinguishing SSLs.

CONCLUSIONS

Muscularis mucosae-based AGRN immunostaining is a novel biomarker to distinguish SSL from HP, TSA, and TA, with a specificity of 97.1% and sensitivity of 98.9% and can assist in diagnosis of morphologically challenging colonic polyps.

ACR Appropriateness Criteria® Colorectal Cancer Screening

This review summarizes the relevant literature regarding colorectal screening with imaging. For individuals at average or moderate risk for colorectal cancer, CT colonography is usually appropriate for colorectal cancer screening. After positive results on a fecal occult blood test or immunohistochemical test, CT colonography is usually appropriate for colorectal cancer detection. For individuals at high risk for colorectal cancer (eg, hereditary nonpolyposis colorectal cancer, ulcerative colitis, or Crohn colitis), optical colonoscopy is preferred because of its ability to obtain biopsies to detect dysplasia. After incomplete colonoscopy, CT colonography is usually appropriate for colorectal cancer screening for individuals at average, moderate, or high risk. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Molecular Diagnostics in Colorectal Carcinoma: Advances and Applications for 2018

The molecular pathogenesis and classification of colorectal carcinoma are based on the traditional adenomaecarcinoma sequence, serrated polyp pathway, and microsatellite instability (MSI). The genetic basis for hereditary nonpolyposis colorectal cancer is the detection of mutations in the MLH1, MSH2, MSH6, PMS2, and EPCAM genes. Genetic testing for Lynch syndrome includes MSI testing, methylator phenotype testing, BRAF mutation testing, and molecular testing for germline mutations in MMR genes. Molecular makers with predictive and prognostic implications include quantitative multigene reverse transcriptase polymerase chain reaction assay and KRAS and BRAF mutation analysis. Mismatch repair-deficient tumors have higher rates of programmed death-ligand 1 expression. Cell-free DNA analysis in fluids are proving beneficial for diagnosis and prognosis in these disease states towards effective patient management.

How the BRAF V600E Mutation Defines a Distinct Subgroup of Colorectal Cancer: Molecular and Clinical Implications

The BRAF oncogene is an integral component of the MAP kinase pathway, and an activating V600E mutation occurs in 15% of sporadic colorectal cancer. This is an early event in serrated pathway tumourigenesis, and the BRAF V600E has been commonly associated with the CpG island methylator phenotype, microsatellite instability (MSI), and a consistent clinical presentation including a proximal location and predilection for elderly females. A proportion of the BRAF mutant lesions remain as microsatellite stable (MSS), and in contrast to the MSI cancers, they have an aggressive phenotype and correlate with poor patient outcomes. Recent studies have found that they have clinical and molecular features of both the BRAF mutant/MSI and the conventional BRAF wild-type cancers and comprise a distinct colorectal cancer subgroup. This review highlights the importance of the BRAF mutation occurring in colorectal cancer stratified for molecular background and discusses its prognostic and clinical significance.

Clinical, Histologic, and Immunophenotypic Features of Serrated Polyps in Patients With Inflammatory Bowel Disease

Background

Colorectal serrated polyps (SP), which include hyperplastic polyps (HP), sessile serrated adenomas/polyps (SSA/P), and traditional serrated adenomas, are not uncommon and have been implicated to play a role in the pathogenesis in a subset of sporadic colorectal carcinomas; however, their significance in patients with prolonged inflammatory bowel disease (IBD) remains unclear.

Methods

We retrospectively studied the clinicopathologic features, BRAF and β-catenin immunohistochemistry staining patterns in 36 SPs from 28 patients with IBD compared with 40 SPs in patients without IBD.

Results

Eleven SSA/Ps and 25 HPs from IBD and site-matched controls were included. SSA/Ps in the study group were slightly more commonly seen in males (55% vs. 41%, P = 0.7) and older patients (55.2 vs. 47.8 years, P = 0.2) compared to patients with HP. They were moderately larger (7.13 mm vs. 4.83 mm, P = 0.14) and more likely located on the right (63.6% vs. 32%, P = 0.46). Smaller percentage of SSA/Ps showed BRAF staining compared to controls (55.6% vs. 73.3%, P = 0.41) and HPs showed similar features (52.0% vs. 54.2%, P = 1). β-catenin was negative in all cases. During follow-up, only one patient in the SSA/P group developed carcinoma 42 months after at the same site and two developed adenoma-like low-grade dysplasia but no patients with HPs had such findings.

Conclusions

Our findings show that SPs in IBD share similar clinicodemographic and immunophenotypical features with sporadic SPs. However, patients with SSA/Ps may have a slight increase in risk of developing dysplasia compared to patients with HPs in IBD.

Endoscopic analysis of colorectal serrated lesions with cancer

Serrated lesions, including hyperplastic polyps (HPs), traditional serrated adenomas (TSAs) and sessile serrated adenomas/polyps (SSA/Ps), are important contributors to colorectal carcinogenesis. The aim of the present study was to analyze the potential of conventional endoscopy and advanced endoscopic imaging techniques to delineate the characteristic features of serrated lesions with cancer. The present study was a retrospective analysis of the data of 168 patients who had undergone colonoscopy, and a total of 228 serrated lesions (77 HPs, 58 TSAs, 84 SSA/Ps, 9 SSA/P plus TSAs) have been identified in these patients. A cancer component was identified in 2.6% of HPs, 13.8% of TSAs and 10.7% of SSA/Ps, but none of SSA/P plus TSAs. Compared with the lesions without cancer, the lesions with cancer exhibited a larger size (HP, TSA and SSA/P), a reddish appearance (SSA/P), a two-tier raised appearance (HP and SSA/P), a central depression (HP, TSA and SSA/P), the type V pit pattern (HP, TSA and SSA/P), and/or the type III capillary pattern (TSA and SSA/P). Deep invasion was identified in 50.0% of HPs, 12.5% of TSAs and 55.6% of SSA/Ps with cancer. The Ki-67 proliferative zone was distributed diffusely within the area of the cancer, but partially within the non-cancer area of HPs, TSAs and SSA/Ps. The lesion types were also analyzed on the basis of mucin phenotype. The present study suggested that a detailed endoscopic analysis of serrated lesions with cancer is useful for delineating characteristic features, and the analysis aids treatment selection.

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.

Precision Medicine for CRC Patients in the Veteran Population: State-of-the-Art, Challenges and Research Directions

Colorectal cancer (CRC) accounts for ~9% of all cancers in the Veteran population, a fact which has focused a great deal of the attention of the VA's research and development efforts. A field-based meeting of CRC experts was convened to discuss both challenges and opportunities in precision medicine for CRC. This group, designated as the VA Colorectal Cancer Cell-genomics Consortium (VA4C), discussed advances in CRC biology, biomarkers, and imaging for early detection and prevention. There was also a discussion of precision treatment involving fluorescence-guided surgery, targeted chemotherapies and immunotherapies, and personalized cancer treatment approaches. The overarching goal was to identify modalities that might ultimately lead to personalized cancer diagnosis and treatment. This review summarizes the findings of this VA field-based meeting, in which much of the current knowledge on CRC prescreening and treatment was discussed. It was concluded that there is a need and an opportunity to identify new targets for both the prevention of CRC and the development of effective therapies for advanced disease. Also, developing methods integrating genomic testing with tumoroid-based clinical drug response might lead to more accurate diagnosis and prognostication and more effective personalized treatment of CRC.

Proximal Sessile Serrated Adenomas Are More Prevalent in Caucasians, and Gastroenterologists Are Better Than Nongastroenterologists at Their Detection

Background and Aim

Proximal sessile serrated adenomas (PSSA) leading to colorectal cancer (CRC) represent an alternate pathway for CRC development. In this study, we aim to determine the prevalence of PSSAs and the impact of patient, colonoscopy, and endoscopist-related factors on PSSA detection.

Methods

Patients ≥ 50 years of age undergoing a screening colonoscopy between 2012 and 2014 were included. Detection rates based on patient gender, race, colonoscopy timing, fellow participation, bowel preparation quality, and specialty of the endoscopist were calculated. t-tests were used to compare detection rates and a multivariate-adjusted analysis was performed.

Results

140 PSSAs were detected from 4151 colonoscopies, with a prevalence of 3.4%. Detection rate was higher in Caucasians compared to African-Americans (AA) (3.7 ± 4.1 versus 0.96 ± 3.5; p < 0.001). Gastroenterologists detected more PSSAs compared to nongastroenterologists (3.9 ± 3.5 versus 2.2 ± 3.0; p = 0.028). These findings were still significant after adjusted multivariate analysis. The rest of the factors did not make significant difference in PSSA detection rate.

Conclusions

PSSAs are more prevalent in Caucasians compared to AAs. Racial difference in prevalence of PSSAs is intriguing and warrants further investigation. Gastroenterologists have a significantly higher PSSADR compared to nongastroenterologists. Educational measures should be implemented in nongastroenterologists to improve their PSSA detection rates.

Current Tissue Molecular Markers in Colorectal Cancer: A Literature Review

BACKGROUND

Colorectal cancer (CRC) is one of the most spread neoplasia types all around the world, especially in western areas. It evolves from precancerous lesions and adenomatous polyps, through successive genetic and epigenetic mutations. Numerous risk factors intervene in its development and they are either environmental or genetic.

AIM OF THE REVIEW

Alongside common screening techniques, such as fecal screening tests, endoscopic evaluation, and CT-colonography, we have identified the most important and useful biomarkers and we have analyzed their role in the diagnosis, prevention, and prognosis of CRC.

CONCLUSION

Biomarkers can become an important tool in the diagnostic and therapeutic process for CRC. But further studies are needed to identify a noninvasive, cost-effective, and highly sensible and specific screening test for their detection and to standardize their use in clinical practice.

The Serrated Polyp Pathway: Is It Time to Alter Surveillance Guidelines?

PURPOSE OF REVIEW

In this manuscript, we review current surveillance guidelines for serrated polyps (SPs) and discuss how recent studies inform the selection of appropriate surveillance intervals for patients with SPs.

RECENT FINDINGS

Large and/or proximal SPs, particularly sessile serrated polyps (SSPs), are associated with increased risk of both synchronous and metachronous neoplasia, including advanced adenomas and colorectal cancer (CRC). Persons harboring multiple SSPs or dysplastic SSPs are at the highest risk. Moreover, a high percentage of large and/or proximal SPs are reclassified as SSPs when read by trained gastrointestinal pathologists, even if they were originally reported as hyperplastic polyps. These findings support the adoption of surveillance guidelines that prescribe closer surveillance of large and/or proximal SPs, regardless of subtype. SSPs remain a challenge to reliably identify, resect, and diagnose via histology. The increased risk of future neoplasia in patients with SSPs is likely driven by a combination of underdetection, inadequate removal, misclassification, and biology. Until further evidence emerges, we support guidelines that recommend close surveillance of patients with a history of large and/or proximal SPs and SSPs specifically in order to mitigate the threat of interval CRC.

Hereditary or sporadic polyposis syndromes

Polyposis syndromes are encountered in endoscopy practice, and are considered rare entities, accounting for ≤1% of colorectal cancer. Polyposis can occur within inherited syndromes or as "sporadic" cases of unknown etiology. Their proper characterization is relevant for patient management, and should nowadays drive appropriate genetic tests which have a key role in clinical practice for driving surveillance and colorectal cancer prevention, enlarged to relatives. Polyposis classification is based upon polyp number and histology, familial and personal history. This review will explore the polyposis nosology and their genetic determinants in the emerging scenario of Next Generation Sequencing which allow testing multiples genes in parallel. This capability will likely continue to increase the range of polyposis predisposing genes, contributing to define new clinical entities.

Histological and molecular classification of gastrointestinal polyps

Endoscopic diagnosis and treatment for gastrointestinal polyps became widely available within the last decades. Exact terminology is important for further therapeutic steps, follow up or treatment. Gastroenterologists, Oncologists, Surgeons and Pathologists need to be aware of the most recent terminology to ensure proper risk assessment and subsequent treatment if necessary. This manuscript aims to list the variety of gastrointestinal polyps and the molecular background where appropriate.

MCM2 expression in serrated polyps demonstrates aberrant cellular proliferation

In normal colonic epithelium, the proliferative zone is limited to the lower half of the colonic crypt. Evaluating the changes in the colonic epithelial proliferation can be useful in understanding pathophysiology of various diseases. Our aim was to investigate the proliferative compartment of serrated polyps (SPs) using MCM2, a protein involved in DNA replication, and assess for changes along the SP spectrum. Immunohistochemistry was performed on serrated polyps (16 microvesicular-type hyperplastic polyps (HP), 58 sessile serrated adenomas (SSA), 7 SSAs with dysplasia) and 6 sections of normal colon using anti-MCM2 antibody. Multiple sections of normal colon showed the following pattern for MCM2 and Ki-67 staining: positive nuclear staining of the lower half of the colonic crypts and/or slightly expanded to the lower two-thirds of the crypt. By MCM2, SPs show expansion of the proliferative compartments; 81.3% of HPs and 100% of SSAs showed some degree of full crypt MCM2 staining. SSAs with dysplasia showed consistent diffuse polyp staining. Aberrant staining in adjacent normal mucosa was also seen in SSAs with dysplasia and in a subset of non-dysplastic SSAs. By using MCM2, we show that serrated polyps exhibit changes in proliferation during progression along the pathway. HPs and SSAs show a similar highly proliferative profile. Aberrant proliferative cell staining patterns in adjacent normal colonic mucosa as seen in SSAs with dysplasia and a subset of SSAs suggest a field effect phenomenon. This indicates that changes in the colonic micro-environment may promote adenoma morphogenesis and predisposition to malignancy.

The clinical impact of serrated colorectal polyps

Serrated polyps (SPs) of the colorectum pose a novel challenge to practicing gastroenterologists. Previously thought benign and unimportant, there is now compelling evidence that SPs are responsible for a significant percentage of incident colorectal cancer worldwide. In contrast to conventional adenomas, which tend to be slow growing and polypoid, SPs have unique features that undermine current screening and surveillance practices. For example, sessile serrated polyps (SSPs) are flat, predominately right-sided, and thought to have the potential for rapid growth. Moreover, SSPs are subject to wide variations in endoscopic detection and pathologic interpretation. Unfortunately, little is known about the natural history of SPs, and current guidelines are based largely on expert opinion. In this review, we outline the current taxonomy, epidemiology, and management of SPs with an emphasis on the clinical and public health impact of these lesions.

Lifetime alcohol intake is associated with an increased risk of KRAS+ and BRAF-/KRAS- but not BRAF+ colorectal cancer

Ethanol in alcoholic beverages is a causative agent for colorectal cancer. Colorectal cancer is a biologically heterogeneous disease, and molecular subtypes defined by the presence of somatic mutations in BRAF and KRAS are known to exist. We examined associations between lifetime alcohol intake and molecular and anatomic subtypes of colorectal cancer. We calculated usual alcohol intake for 10-year periods from age 20 using recalled frequency and quantity of beverage-specific consumption for 38,149 participants aged 40-69 years from the Melbourne Collaborative Cohort Study. Cox regression was performed to derive hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between lifetime alcohol intake and colorectal cancer risk. Heterogeneity in the HRs across subtypes of colorectal cancer was assessed. A positive dose-dependent association between lifetime alcohol intake and overall colorectal cancer risk (mean follow-up = 14.6 years; n = 596 colon and n = 326 rectal cancer) was observed (HR = 1.08, 95% CI: 1.04-1.12 per 10 g/day increment). The risk was greater for rectal than colon cancer (p_homogeneity  = 0.02). Alcohol intake was associated with increased risks of KRAS+ (HR = 1.07, 95% CI: 1.00-1.15) and BRAF-/KRAS- (HR = 1.05, 95% CI: 1.00-1.11) but not BRAF+ tumors (HR = 0.89, 95% CI: 0.78-1.01; p_homogeneity  = 0.01). Alcohol intake is associated with an increased risk of KRAS+ and BRAF-/KRAS- tumors originating via specific molecular pathways including the traditional adenoma-carcinoma pathway but not with BRAF+ tumors originating via the serrated pathway. Therefore, limiting alcohol intake from a young age might reduce colorectal cancer originating via the traditional adenoma-carcinoma pathway.

Gastric Proteins MUC5AC and TFF1 as Potential Diagnostic Markers of Colonic Sessile Serrated Adenomas/Polyps

OBJECTIVES

A subset of colon cancers originates from sessile serrated adenomas/polyps (SSA/Ps). Our goal was to identify markers for SSA/Ps that could aid in distinguishing them from hyperplastic polyps (HPs).

METHODS

We performed immunostaining for gastric proteins MUC5AC and TFF1 in formalin-fixed, paraffin-embedded (FFPE) samples of HPs (n = 47), SSA/Ps (n = 37), and normal colon (n = 30).

RESULTS

Control mucosa expressed only trace amounts of MUC5AC and TFF1. HPs exhibited an 11.3- and 11.4-fold increase in MUC5AC and TFF1 expression confined to the upper segments of the crypts near the luminal surface of the polyps. SSA/Ps displayed on average 1.6-fold (MUC5AC, P  < .008) and 1.4-fold (TFF1, P  < .03) higher signal intensity for these markers than HPs, with a dramatic coexpression of MUC5AC and TFF1 typically occupying the entire length of the crypt. Immunoperoxidase results were similar to immunofluorescence staining for both MUC5AC and TFF1.

CONCLUSIONS

Our results suggest that the analysis of expression of MUC5AC and TFF1 may be useful for differentiating SSA/Ps from HPs. We also suggest the possibility that crypt morphology may be at least partly due to overproduction of highly viscous gastric mucins and that these proteins may play a role in the serrated pathway to colon carcinogenesis.

Development and Clinical Validation of a Blood Test Based on 29-Gene Expression for Early Detection of Colorectal Cancer

PURPOSE

A blood test for early detection of colorectal cancer is a valuable tool for testing asymptomatic individuals and reducing colorectal cancer-related mortality. The objective of this study was to develop and validate a novel blood test able to differentiate patients with colorectal cancer and adenomatous polyps (AP) from individuals with a negative colonoscopy.

EXPERIMENTAL DESIGN

A case-control, multicenter clinical study was designed to collect blood samples from patients referred for colonoscopy or surgery. Predictive algorithms were developed on 75 controls, 61 large AP (LAP) ≥1 cm, and 45 colorectal cancer cases and independently validated on 74 controls, 42 LAP, and 52 colorectal cancer cases (23 stages I-II) as well as on 245 cases including other colorectal findings and diseases other than colorectal cancer. The test is based on a 29-gene panel expressed in peripheral blood mononuclear cells alone or in combination with established plasma tumor markers.

RESULTS

The 29-gene algorithm detected colorectal cancer and LAP with a sensitivity of 79.5% and 55.4%, respectively, with 90.0% specificity. Combination with the protein tumor markers carcinoembryonic antigen (CEA) and CYFRA21-2 resulted in a specificity increase (92.2%) with a sensitivity for colorectal cancer and LAP detection of 78.1% and 52.3%, respectively.

CONCLUSIONS

We report the validation of a novel blood test, Colox®, for the detection of colorectal cancer and LAP based on a 29-gene panel and the CEA and CYFRA21-1 plasma biomarkers. The performance and convenience of this routine blood test provide physicians a useful tool to test average-risk individuals unwilling to undergo upfront colonoscopy. Clin Cancer Res; 22(18); 4604-11. ©2016 AACR.

Gene Signature in Sessile Serrated Polyps Identifies Colon Cancer Subtype

Sessile serrated colon adenoma/polyps (SSA/P) are found during routine screening colonoscopy and may account for 20% to 30% of colon cancers. However, differentiating SSA/Ps from hyperplastic polyps (HP) with little risk of cancer is challenging and complementary molecular markers are needed. In addition, the molecular mechanisms of colon cancer development from SSA/Ps are poorly understood. RNA sequencing (RNA-Seq) was performed on 21 SSA/Ps, 10 HPs, 10 adenomas, 21 uninvolved colon, and 20 control colon specimens. Differential expression and leave-one-out cross-validation methods were used to define a unique gene signature of SSA/Ps. Our SSA/P gene signature was evaluated in colon cancer RNA-Seq data from The Cancer Genome Atlas (TCGA) to identify a subtype of colon cancers that may develop from SSA/Ps. A total of 1,422 differentially expressed genes were found in SSA/Ps relative to controls. Serrated polyposis syndrome (n = 12) and sporadic SSA/Ps (n = 9) exhibited almost complete (96%) gene overlap. A 51-gene panel in SSA/P showed similar expression in a subset of TCGA colon cancers with high microsatellite instability. A smaller 7-gene panel showed high sensitivity and specificity in identifying BRAF-mutant, CpG island methylator phenotype high, and MLH1-silenced colon cancers. We describe a unique gene signature in SSA/Ps that identifies a subset of colon cancers likely to develop through the serrated pathway. These gene panels may be utilized for improved differentiation of SSA/Ps from HPs and provide insights into novel molecular pathways altered in colon cancer arising from the serrated pathway. Cancer Prev Res; 9(6); 456-65. ©2016 AACR.

Systematic meta-analyses and field synopsis of genetic association studies in colorectal adenomas

BACKGROUND

Low penetrance genetic variants, primarily single nucleotide polymorphisms, have substantial influence on colorectal cancer (CRC) susceptibility. Most CRCs develop from colorectal adenomas (CRA). Here we report the first comprehensive field synopsis that catalogues all genetic association studies on CRA, with a parallel online database [http://www.chs.med.ed.ac.uk/CRAgene/].

METHODS

We performed a systematic review, reviewing 9750 titles, and then extracted data from 130 publications reporting on 181 polymorphisms in 74 genes. We conducted meta-analyses to derive summary effect estimates for 37 polymorphisms in 26 genes. We applied the Venice criteria and Bayesian False Discovery Probability (BFDP) to assess the levels of the credibility of associations.

RESULTS

We considered the association with the rs6983267 variant at 8q24 as 'highly credible', reaching genome-wide statistical significance in at least one meta-analysis model. We identified 'less credible' associations (higher heterogeneity, lower statistical power, BFDP > 0.02) with a further four variants of four independent genes: MTHFR c.677C>T p.A222V (rs1801133), TP53 c.215C>G p.R72P (rs1042522), NQO1 c.559C>T p.P187S (rs1800566), and NAT1 alleles imputed as fast acetylator genotypes. For the remaining 32 variants of 22 genes for which positive associations with CRA risk have been previously reported, the meta-analyses revealed no credible evidence to support these as true associations.

CONCLUSIONS

The limited number of credible associations between low penetrance genetic variants and CRA reflects the lower volume of evidence and associated lack of statistical power to detect associations of the magnitude typically observed for genetic variants and chronic diseases. The CRA gene database provides context for CRA genetic association data and will help inform future research directions.

The frequency of early colorectal cancer derived from sessile serrated adenoma/polyps among 1858 serrated polyps from a single institution

BACKGROUND AND AIM

Sessile serrated adenoma/polyps (SSAPs) are suspected to have a high malignant potential, although few reports have evaluated the incidence of carcinomas derived from SSAPs using the new classification for serrated polyps (SPs). The aim of study was to compare the frequency of cancer coexisting with the various SP subtypes including mixed polyps (MIXs) and conventional adenomas (CADs).

METHODS

A total of 18,667 CADs were identified between April 2005 and December 2011, and 1858 SPs (re-classified as SSAP, hyperplastic polyp (HP), traditional serrated adenoma (TSA), or MIX) were removed via snare polypectomy, endoscopic mucosal resection, or endoscopic sub-mucosal dissection.

RESULTS

Among 1160 HP lesions, 1 (0.1%) coexisting sub-mucosal invasive carcinoma (T1) was detected. Among 430 SSAP lesions, 3 (0.7%) high-grade dysplasia (HGD/Tis) and 1 (0.2%) T1 were detected. All of the lesions were detected in the proximal colon, with a mean tumor diameter of 18 mm (SD 9 mm). Among 212 TSA lesions, 3 (1%) HGD/Tis were detected but no T1 cancer. Among 56 MIX lesions, 9 (16%) HGD/Tis and 1 (2%) T1 cancers were detected, and among 18,677 CAD lesions, 964 (5%) HGD/Tis and 166 (1%) T1 cancers were identified.

CONCLUSIONS

Among the resected lesions that were detected during endoscopic examination, a smaller proportion (1%) of SSAPs harbored HGD or coexisting cancer, compared to CAD or MIX lesions. Therefore, more attention should be paid to accurately identifying lesions endoscopically for intentional resection and the surveillance of each SP subtype.

Molecular pathogenesis of sporadic colorectal cancers

Colorectal cancer (CRC) results from the progressive accumulation of genetic and epigenetic alterations that lead to the transformation of normal colonic mucosa to adenocarcinoma. Approximately 75% of CRCs are sporadic and occur in people without genetic predisposition or family history of CRC. During the past two decades, sporadic CRCs were classified into three major groups according to frequently altered/mutated genes. These genes have been identified by linkage analyses of cancer-prone families and by individual mutation analyses of candidate genes selected on the basis of functional data. In the first half of this review, we describe the genetic pathways of sporadic CRCs and their clinicopathologic features. Recently, large-scale genome analyses have detected many infrequently mutated genes as well as a small number of frequently mutated genes. These infrequently mutated genes are likely described in a limited number of pathways. Gene-oriented models of CRC progression are being replaced by pathway-oriented models. In the second half of this review, we summarize the present knowledge of this research field and discuss its prospects.

Serrated colorectal polyps in inflammatory bowel disease

Serrated colorectal polyps, which, besides hyperplastic polyps, comprise sessile serrated adenomas/polyps and traditional serrated adenomas, are presumptive precursors of at least 20% of sporadic colorectal carcinomas; however, their significance in patients with inflammatory bowel disease is unclear. We retrospectively evaluated 78 serrated polyps, removed over a 14-year period from 6602 inflammatory bowel disease patients undergoing endoscopic surveillance, with respect to morphologic, clinicopathologic, and molecular features, and compared rates of advanced neoplasia (high-grade dysplasia and carcinoma) development following the index serrated polyp diagnosis to reference inflammatory bowel disease cohorts without serrated polyps. Serrated polyps negative for dysplasia, which morphologically resembled sporadic sessile serrated adenoma/polyps, occurred mainly in females, in the proximal colon, and contained BRAF mutations. Serrated polyps with low-grade dysplasia resembled sporadic traditional serrated adenomas and occurred mainly in males, in the distal colon, and contained KRAS mutations. Serrated polyps indefinite for dysplasia were morphologically heterogeneous, but similar to serrated polyps positive for low-grade dysplasia with respect to male predominance, left-sided location, and KRAS mutation rates. Rates of prevalent neoplasia associated with serrated polyps positive for low-grade dysplasia, indefinite for dysplasia, and negative for dysplasia were 76, 39, and 11%, respectively (P<0.001). Actuarial 10-year rates of incident advanced neoplasia after an initial diagnosis of serrated polyp positive for low-grade dysplasia, indefinite for dysplasia, and negative for dysplasia were 17, 8, and 0%, respectively, the first and last being significantly different (P=0.02) and comparable to those of corresponding reference populations of inflammatory bowel disease patients with and without low-grade dysplasia at baseline, respectively. We conclude that in serrated polyps from inflammatory bowel disease patients, dysplasia grade correlates with morphology, sex, anatomic location, BRAF and KRAS mutation status, prevalent conventional neoplasia, and rates of advanced neoplasia development.

High-risk metachronous polyps are more frequent in patients with traditional serrated adenomas than in patients with conventional adenomas: a multicenter prospective study

BACKGROUND AND AIMS

Although the malignant progression of serrated polyps has been clearly documented, the malignant potential of the traditional serrated adenoma (TSA) subtype has not been established. We compared the prevalence of metachronous polyps in surveillance colonoscopies between patients with TSA and those with conventional adenomas (CAs).

METHODS

Four hundred twenty patients were diagnosed with TSAs by current diagnostic criteria at 10 tertiary care university hospitals in Korea from January 2003 to December 2005; 186 patients who received surveillance colonoscopy after removal of initial polyps were enrolled. During the same time period, 372 age- and sex-matched patients diagnosed with CAs were used as a control group.

RESULTS

TSA patients had a significantly higher recurrence rate of colorectal polyps compared with CA patients (66.1% vs 43.5%, respectively). TSA patients had a greater number (3 vs 2) and larger size (8.6 ± 5.7 vs 6.3 ± 5.2 mm) of recurrent polyps compared with CA patients. TSA patients also had a higher rate of CA (54.8% vs 37.9%), serrated adenoma (14.0% vs. 0.8%), and hyperplastic polyp (33.3% vs. 13.7%) recurrence compared with CA patients. TSA patients had significantly greater odds of having a recurrent high-risk polyp than CA patients (odds ratio, 2.37; 95% confidence interval, 1.55-3.63).

CONCLUSIONS

In comparison with patients with CAs, patients with TSAs have a higher metachronous occurrence rate of all polyp subtypes including CAs, serrated adenomas, and hyperplastic polyps. Moreover, the presence of TSAs is an independent predictor of a high-risk polyp occurrence.

Long-Term Impact of the Dutch Colorectal Cancer Screening Program on Cancer Incidence and Mortality-Model-Based Exploration of the Serrated Pathway

BACKGROUND

We aimed to predict the long-term colorectal cancer incidence, mortality, and colonoscopy demand of the recently implemented Dutch colorectal cancer screening program.

METHODS

The Adenoma and Serrated pathway to Colorectal Cancer model was set up to simulate the Dutch screening program consisting of biennial fecal immunochemical testing combined with the new Dutch surveillance guidelines, between 2014 and 2044. The impact of screening and surveillance was evaluated under three sets of natural history assumptions differing in the contribution of the serrated pathway to colorectal cancer incidence. In sensitivity analyses, other assumptions concerning the serrated pathway were varied. Model-predicted outcomes were yearly colorectal cancer incidence, mortality, and colonoscopy demand per year.

RESULTS

Assuming an aging population, colorectal cancer incidence under 30 years of screening is predicted to decrease by 35% and 31% for a contribution of 0% and 30% of the serrated pathway to colorectal cancer, respectively. For colorectal cancer mortality, reductions are 47% and 45%. In 2044, 110,000 colonoscopies will be required annually assuming no contribution of the serrated pathway (27 per 1,000 individuals in the screening age range). Including the serrated pathway influences predicted screening effectiveness if serrated lesions are neither detected nor treated at colonoscopy, and/or if colorectal cancers arising from serrated lesions have substantially lower survival rates than those arising from adenomas.

CONCLUSIONS

The Dutch screening program will markedly decrease colorectal cancer incidence and mortality but considerable colonoscopy resources will be required.

IMPACT

Predictions of long-term screening effectiveness are preferably based on both pathways to colorectal cancer to transparently describe the impact of uncertainties regarding the serrated pathway on long-term predictions.

Cancer emerging from the recurrence of sessile serrated adenoma/polyp resected endoscopically 5 years ago

Since the serrated neoplastic pathway has been regarded as an important pathway of colorectal carcinogenesis, few reports have been published on clinical cases of cancer derived from sessile serrated adenoma/polyp, especially on recurrence after resected sessile serrated adenoma/polyp. An elderly woman underwent endoscopic mucosal resection of a flat elevated lesion, 30 mm in diameter, in the ascending colon; the histopathological diagnosis at that time was a hyperplastic polyp, now known as sessile serrated adenoma/polyp. Five years later, cancer due to the malignant transformation of the sessile serrated adenoma/polyp was detected at the same site. The endoscopic diagnosis was a deep invasive carcinoma with a remnant sessile serrated adenoma/polyp component. The carcinoma was surgically removed, and the pathological diagnosis was an adenocarcinoma with sessile serrated adenoma/polyp, which invaded the muscularis propria. The surgically removed lesion did not have a B-RAF mutation in either the sessile serrated adenoma/polyp or the carcinoma; moreover, the initial endoscopically resected lesion also did not have a B-RAF mutation. Immunohistochemistry confirmed negative MLH1 protein expression in only the cancer cells. Lynch syndrome was not detected on genomic examination. The lesion was considered to be a cancer derived from sessile serrated adenoma/polyp recurrence after endoscopic resection, because both the surgically and endoscopically resected lesions were detected at the same location and had similar pathological characteristics, with a serrated structure and low-grade atypia. Furthermore, both lesions had a rare diagnosis of a sessile serrated adenoma/polyp without B-RAF mutation. This report highlights the need for the follow-up colonoscopy after endoscopic resection and rethinking our resection procedures to improve treatment.

Molecular and histologic considerations in the assessment of serrated polyps

CONTEXT : Colorectal cancer is a heterogeneous disease resulting from different molecular pathways of carcinogenesis. Recent data evaluating the histologic features and molecular basis of the serrated polyp-carcinoma pathway have significantly contributed to more comprehensive classifications of and treatment recommendations for these tumors.

OBJECTIVE

To integrate the most recent molecular findings in the context of histologic classifications of serrated lesions and their implications in diagnostic pathology and colorectal cancer surveillance.

DATA SOURCES

Published literature focused on serrated polyps and their association with colorectal cancer.

CONCLUSIONS

Three types of serrated polyps are currently recognized: hyperplastic polyps, sessile serrated adenomas/polyps, and traditional serrated adenomas. The BRAF V600E mutation is one of the most frequent molecular abnormalities identified in hyperplastic polyps and sessile serrated adenomas. In contrast, in traditional serrated adenomas, either BRAF V600E or KRAS mutations can be frequently identified. CpG methylation has emerged as a critical molecular mechanism in the sessile serrated pathway. CpG methylation of MLH1 often leads to reduced or lost expression in dysplastic foci and carcinomas arising in sessile serrated adenomas/polyps.

Associations among pericolonic fat, visceral fat, and colorectal polyps on CT colonography

OBJECTIVE

To determine the association between pericolonic fat and colorectal polyps using CT colonography (CTC).

METHODS

A total of 1169 patients who underwent CTC and optical colonoscopy on the same day were assessed. Pericolonic fat was measured on CTC in a band surrounding the colon. Visceral adipose tissue volume was measured at the L2-L3 levels. Student's t-tests, odds ratio, logistic regression, binomial statistics, and weighted kappa were performed to ascertain associations with the incidence of colorectal polyps.

RESULTS

Pericolonic fat volume fractions (PFVF) were 61.5 ± 11.0% versus 58.1 ± 11.5%, 61.6 ± 11.1% versus 58.7 ± 11.5%, and 62.4 ± 10.6% versus 58.8 ± 11.5% for patients with and without any polyps, adenomatous polyps, and hyperplastic polyps, respectively (P<0.0001). Similar trends were observed when examining visceral fat volume fractions (VFVF). When patients were ordered by quintiles of PFVF or VFVF, there were 2.49-, 2.19-, and 2.39-fold increases in odds ratio for the presence of any polyp, adenomatous polyps, or hyperplastic polyps from the first to the fifth quintile for PFVF and 1.92-, 2.00-, and 1.71-fold increases in odds ratio for VFVF. Polyps tended to occur more commonly in parts of the colon that had more PFVF than the spatially adjusted average for patients in the highest quintile of VFVF.

CONCLUSIONS

Pericolonic fat accumulations, like visceral fat, are correlated with an increased risk of adenomatous and hyperplastic polyps.

BRAF vs RAS oncogenes: are mutations of the same pathway equal? Differential signalling and therapeutic implications

As the increased knowledge of tumour heterogeneity and genetic alterations progresses, it exemplifies the need for further personalized medicine in modern cancer management. Here, the similarities but also the differential effects of RAS and BRAF oncogenic signalling are examined and further implications in personalized cancer diagnosis and therapy are discussed. Redundant mechanisms mediated by the two oncogenes as well as differential regulation of signalling pathways and gene expression by RAS as compared to BRAF are addressed. The implications of RAS vs BRAF differential functions, in relevant tumour types including colorectal cancer, melanoma, lung cancer are discussed. Current therapeutic findings and future viewpoints concerning the exploitation of RAS-BRAF-pathway alterations for the development of novel therapeutics and efficient rational combinations, as well as companion tests for relevant markers of response will be evaluated. The concept that drug-resistant cells may also display drug dependency, such that altered dosing may prevent the emergence of lethal drug resistance posed a major therapy hindrance.

Adenocarcinoma arising in small sessile serrated adenoma/polyp (SSA/P) of the colon: clinicopathological study of eight lesions

We reviewed the clinicopathological findings of eight cases of sessile serrated adenoma/polyps (SSA/Ps) with carcinoma, the largest diameter of which was 10 mm or less. All lesions were polyps located in the right side of the colon. Four lesions showed submucosal invasion and one lesion invaded the proper muscle layer. The depth of invasion, however, did not seem to be related to the carcinoma area size. Most carcinomas were well to moderately differentiated tubular adenocarcinomas focally showing some serrated appearances, and the predominant component of one carcinoma was a poorly differentiated medullary growth with inflammatory stroma. Rapid progression to invasive carcinoma from SSA/P was suggested for the carcinoma with proper muscle invasion whereas one submucosally invasive carcinoma was considered to progress over 7 years. Immunohistochemically, it was suggested that with or without hMLH1 protein loss, alterations of p53 and/or Wnt signaling pathway can be involved in the cancerization through SSA/Ps. The carcinomas irregularly imitated the mucin expression of the SSA/Ps (positive for MUC5AC and MUC2, and MUC6 expression in crypt bases), which was lost with progression of the carcinomas. Analyses of small SSA/P lesions with cancerization would facilitate the understanding of the mode of progression of SSA/Ps and their early detection.

Colorectal serrated pathway cancers and precursors

The serrated pathway (SP) can be viewed as two parallel, but partially overlapping, arrays of colorectal precursor lesions, and their respective endpoint carcinomas, that are distinct from those of the conventional adenoma-carcinoma sequence (APC-pathway). In this review we focus at the outset on the clinical impact, pathological features, molecular genetics and biological behaviours of the various SP cancers. Then we summarize the clinicopathological features, classification and molecular profiles of the two main precursor lesions that anchor the respective pathways: (i) sessile serrated adenoma/polyp (SSA/P), also called sessile serrated lesion (SSL), and (ii) traditional serrated adenoma (TSA). Activating mutations of the RAS-RAF-MAPK pathway initiate and sustain the lesions of the SP, and CpG island methylation of the promoter regions of tumour suppressor and DNA repair genes play the major role in their neoplastic progression. The SP includes microsatellite stable (MSS) carcinomas that are among the most biologically aggressive colorectal carcinomas (CRC), and also accounts for the great preponderance of sporadic hypermutated, mismatch repair (MMR)-deficient or microsatellite instable (MSI) CRC. The identification, removal and appropriate classification of at-risk SP precursors and surveillance of individuals who harbour these lesions present a challenge and opportunity for CRC prevention and mortality reduction.

Risk factors for serrated polyps of the colorectum

Serrated pathway polyps are a relatively new area of interest in the field of colorectal cancer screening and prevention. Akin to conventional adenomas, some serrated polyps (SPs) have the potential to develop into malignant serrated neoplasms, yet little is known regarding risk factors for these lesions. Early epidemiological studies of hyperplastic polyps were performed without knowledge of the serrated pathway and likely included a mixture of SPs. More recently, studies have specifically evaluated premalignant SPs, such as the sessile serrated adenoma (SSA) or surrogates for these polyps such as large or proximally located SPs. SPs share some risk factors with conventional adenomas and have been associated with tobacco use, obesity, and age. Nonsteroidal anti-inflammatory drug (NSAID) use, fiber, folic acid, and calcium have been associated with reduced risk of SPs. Studies focused on SSAs specifically have reported associations with age, female sex, smoking, obesity, diabetes, and possibly diets high in fat, carbohydrates, and calories. Higher education has also been associated with risk of SSAs, while an inverse association between NSAID use and SSAs has been reported. Risk factors for traditional serrated adenomas are largely unknown. Studies are largely limited by varying inclusion criteria, as well as differences in pathological classification schemes. Further epidemiological studies of SPs are needed to aid in risk stratification and screening, and etiological research.

Histological overlap between colorectal villous/tubulovillous and traditional serrated adenomas

AIMS

To ascertain the degree of histological overlap between conventional villous/tubulovillous (VA/TVAs) and traditional serrated adenomas (TSA).

METHODS AND RESULTS

A total of 180 polyps from the left colon/rectum diagnosed as VA/TVAs were retrieved randomly and reviewed by five pathologists looking specifically at luminal serration, cytoplasmic eosinophilia and the presence of ectopic crypt foci (ECF). For comparative purposes, 100 tubular adenomas and 80 TSAs were also examined. Twenty VA/TVAs were reclassified as TSA. Luminal serration as noted in TSA was not seen in any of the remaining 160 polyps, ECFs were noted in 55 of the 160 VA/TVAs (34%), while cytoplasmic eosinophilia (constituting <50% of the adenoma) was noted in only 10 of 160 cases (6.2%).

CONCLUSIONS

Ectopic crypt foci and cytoplasmic eosinophilia are encountered in sporadic VA/TVAs but not to the same extent and degree as in TSA. ECFs were found in one-third of cases, but cytoplasmic eosinophilia is rare. The pattern of luminal serration in TSA is very characteristic and not recapitulated in VA/TVA. The occurrence of all three histological features together occurs only in TSA. ECFs are not a sine qua non for TSA and are encountered commonly in VA/TVAs. VA/TVAs often contain occasional glands typical of TSA.

[In situ analyses of molecular mechanisms of colorectal carcinogenesis]

The main signaling pathways of colorectal carcinogenesis encompass the classical adenoma-carcinoma sequence and the serrated route. In the classical adenoma-carcinoma sequence there are initially frequent mutations of the APC gene which lead to an activation of the WNT signaling pathway. When the WNT signaling pathway is activated β-catenin mediates the transcription of diverse factors which cause migration, invasion and proliferation of cells. Although APC mutations occur in all tumor cells, a heterogeneous distribution pattern of β-catenin is found in tumors and β-catenin also represents an important prognostic marker. A similar picture is found for γ-catenin which is expressed independently from β-catenin. Clearly more homogeneous is the expression of TCF4 and LEF1 which are the main binding partners of β-catenin and γ-catenin and are likewise important prognostic markers. The TRAIL signaling pathway is therapeutically interesting and within this pathway loss of the main receptors TRAIL-R1 and TRAIL-R2 is frequently found. Furthermore, the membranous localization of both factors correlates with a better overall survival. These results might be therapeutically relevant with respect to therapy with recombinant TRAIL molecules binding to TRAIL-R1 and TRAIL-R2. In the serrated route oncogen-induced senescence caused by mutations of the KRAS and BRAF oncogenes initially plays an important role. This senescence blockade is overcome by hypermethylation of the p16(INK4a) promoter and leads to the development of invasive tumors. The SIRT1 and c-Myc genes also contribute to progression of lesions in the serrated route and are activated through the RAS/RAF/MAPK-kinase signaling pathway as well as the WNT/β-catenin signaling pathway.

Molecular diagnostics in colorectal carcinoma

Molecular pathogenesis and classification of colorectal carcinoma are based on the adenoma-carcinoma sequence in the Vogelstein model, serrated polyp pathway, and microsatellite instability. The genetic basis for hereditary nonpolyposis colorectal cancer is based on detection of genetic mutations. Genetic testing for Lynch syndrome includes microsatellite instability, methylator phenotyping, BRAF mutation, and molecular testing. Molecular makers include quantitative multigene reverse transcriptase-polymerase chain reaction assay and KRAS and BRAF mutation analysis. Potential biomarkers include one-step nucleic acid amplification and epigenetic inactivation of endothelin 2 and endothelin 3 in colon cancer. Molecular screening approaches in colorectal cancer using stool DNA are under investigation.

Modeling the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA)

Several colorectal cancer (CRC) screening models have been developed describing the progression of adenomas to CRC. Currently, there is increasing evidence that serrated lesions can also develop into CRC. It is not clear whether screening tests have the same test characteristics for serrated lesions as for adenomas, but lower sensitivities have been suggested. Models that ignore this type of colorectal lesions may provide overly optimistic predictions of the screen-induced reduction in CRC incidence. To address this issue, we have developed the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model that includes the adenoma-carcinoma pathway and the serrated pathway to CRC as well as characteristics of colorectal lesions. The model structure and the calibration procedure are described in detail. Calibration resulted in 19 parameter sets for the adenoma-carcinoma pathway and 13 for the serrated pathway that match the age- and sex-specific adenoma and serrated lesion prevalence in the COlonoscopy versus COlonography Screening (COCOS) trial, Dutch CRC incidence and mortality rates, and a number of other intermediate outcomes concerning characteristics of colorectal lesions. As an example, we simulated outcomes for a biennial fecal immunochemical test screening program and a hypothetical one-time colonoscopy screening program. Inclusion of the serrated pathway influenced the predicted effectiveness of screening when serrated lesions are associated with lower screening test sensitivity or when they are not removed. To our knowledge, this is the first model that explicitly includes the serrated pathway and characteristics of colorectal lesions. It is suitable for the evaluation of the (cost)effectiveness of potential screening strategies for CRC.

ACR Appropriateness Criteria colorectal cancer screening

Colorectal cancer is the third leading cause of cancer deaths in the United States. Most colorectal cancers can be prevented by detecting and removing the precursor adenomatous polyp. Individual risk factors for the development of colorectal cancer will influence the particular choice of screening tool. CT colonography (CTC) is the primary imaging test for colorectal cancer screening in average-risk individuals, whereas the double-contrast barium enema (DCBE) is now considered to be a test that may be appropriate, particularly in settings where CTC is unavailable. Single-contrast barium enema has a lower performance profile and is indicated for screening only when CTC and DCBE are not available. CTC is also the preferred test for colon evaluation following an incomplete colonoscopy. Imaging tests including CTC and DCBE are not indicated for colorectal cancer screening in high-risk patients with polyposis syndromes or inflammatory bowel disease. This paper presents the updated colorectal cancer imaging test ratings and is the result of evidence-based consensus by the ACR Appropriateness Criteria Expert Panel on Gastrointestinal Imaging. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Pathological features of the sessile serrated adenoma/polyp with special references of its carcinogenesis

The sessile serrated adenoma/polyp (SSA/P) has been thought as the relatively new precursor for the colorectal cancer. In the current review, the well-known pathological features including the histological definition of the SSA/P are described using the previous reports. Although the SSA/P is thought one of pre-cancerous lesions of the colorectal carcinoma, the decisive or documentary lesion like "carcinoma in adenoma" is very rare. In this review, the strict case of the carcinoma derived from the SSA/P is demonstrated using our cases. Although the genetic investigations of the SSA/P have shown the new pathway of colorectal carcinogenesis and these concepts are thought to be almost right, the verification for them should be performed using "the carcinoma in SSA/P" like the present case.

RNA sequencing of sessile serrated colon polyps identifies differentially expressed genes and immunohistochemical markers

BACKGROUND

Sessile serrated adenomas/polyps (SSA/Ps) may account for 20-30% of colon cancers. Although large SSA/Ps are generally recognized phenotypically, small (<1 cm) or dysplastic SSA/Ps are difficult to differentiate from hyperplastic or small adenomatous polyps by endoscopy and histopathology. Our aim was to define the comprehensive gene expression phenotype of SSA/Ps to better define this cancer precursor.

RESULTS

RNA sequencing was performed on 5' capped RNA from seven SSA/Ps collected from patients with the serrated polyposis syndrome (SPS) versus eight controls. Highly expressed genes were analyzed by qPCR in additional SSA/Ps, adenomas and controls. The cellular localization and level of gene products were examined by immunohistochemistry in syndromic and sporadic SSA/Ps, adenomatous and hyperplastic polyps and controls. We identified 1,294 differentially expressed annotated genes, with 106 increased ≥10-fold, in SSA/Ps compared to controls. Comparing these genes with an array dataset for adenomatous polyps identified 30 protein coding genes uniquely expressed ≥10-fold in SSA/Ps. Biological pathways altered in SSA/Ps included mucosal integrity, cell adhesion, and cell development. Marked increased expression of MUC17, the cell junction protein genes VSIG1 and GJB5, and the antiapoptotic gene REG4 were found in SSA/Ps, relative to controls and adenomas, were verified by qPCR analysis of additional SSA/Ps (n = 21) and adenomas (n = 10). Immunohistochemical staining of syndromic (n≥11) and sporadic SSA/Ps (n≥17), adenomatous (n≥13) and hyperplastic (n≥10) polyps plus controls (n≥16) identified unique expression patterns for VSIG1 and MUC17 in SSA/Ps.

CONCLUSION

A subset of genes and pathways are uniquely increased in SSA/Ps, compared to adenomatous polyps, thus supporting the concept that cancer develops by different pathways in these phenotypically distinct polyps with markedly different gene expression profiles. Immunostaining for a subset of these genes differentiates both syndromic and sporadic SSA/Ps from adenomatous and hyperplastic polyps.