Serrated adenoma of the colorectum: a lesion with teeth

Annexin A10 and HES-1 Immunohistochemistry in Right-sided Traditional Serrated Adenomas Suggests an Origin From Sessile Serrated Adenoma

There is increasing body of evidence to suggest that some colonic serrated polyps do not fit morphologically with any of the proposed categories for serrated polyps recommended by the World Health Organization. Most of these polyps have morphologic features of traditional serrated adenoma (TSA) admixed with areas resembling sessile serrated adenoma (SSA) or hyperplastic polyp (HP). Based on these findings it has been suggested that at least some TSAs may arise in association with precursor HP or SSA lesions, particularly those that develop in right colon. To further evaluate this hypothesis, 39 serrated polyps from right side of the colon (cecum, ascending, and transverse colon) with mixed features of TSA and SSA were evaluated by 2 immunostains previously shown to represent markers of SSA. One is Annexin A10 which shows upregulated expression in SSA and the other is Hes-1 which is shown to be down regulated in SSA. The expression patterns of these markers were evaluated in SSA and TSA components of hybrid polyps and compared with control groups (pure SSAs and TSAs of right colon). SSA component in hybrid polyps did not show any significant difference in staining pattern compared with that seen in TSA component of hybrid polyps or in pure TSA polyps. These findings further support the hypothesis that recognizes SSA as a precursor lesion for TSA in the right colon.

[Immunohistochemical expression of p53, Bcl-2, and Ki-67 proteins in traditional serrated adenomas of colon]

BACKGROUND/AIMS

Serrated adenomas of the colon show mixed characteristics of both hyperplastic and adenomatous polyps. Serrated adenomas are known to progress via the serrated pathway than the adenoma-carcinoma pathway. The aim of this study was to evaluate the characteristics of traditional serrated adenomas compared to hyperplastic polyps and tubular adenomas by using immunohistochemical staining for p53, Bcl-2, and Ki-67.

METHODS

Age, sex, location, size and the immunoexpression of p53, Bcl-2, and Ki-67 were retrospectively analyzed in 20 traditional serrated adenomas, 20 hyperplastic polyps, and 20 tubular adenomas from January 2007 to December 2012 at The Catholic University of Korea, Yeouido St. Mary's Hospital.

RESULTS

There was no difference in Bcl-2 and p53 expression between traditional serrated adenomas and hyperplastic polyps. Ki-67 Expression of traditional serrated adenomas was higher than that of hyperplastic polyps (p=0.001). Ki-67 and p53 expression was similar between traditional serrated and tubular adenomas. Bcl-2 expression of traditional serrated adenomas was lower than that of tubular adenomas (p=0.001). Regarding the expression of p53, Bcl-2, and Ki-67 in traditional serrated adenomas, there were no statistical differences among age, sex, location, and size.

CONCLUSIONS

Our study suggested that Ki-67 may be helpful in distinguishing traditional serrated adenomas from hyperplastic polyps, and p53 expression may be ineffective in distinguishing between traditional serrated and tubular adenomas. From Bcl-2 expression, it is suggested that the tumorigenesis of traditional serrated adenomas is lower than that of tubular adenomas.

Serrated polyposis: prospective study of first-degree relatives

INTRODUCTION

Serrated polyposis (SP) is an infrequent colorectal cancer (CRC) predisposition syndrome. An unidentified genetic defect is believed to play a role in this condition. The risk of SP and/or CRC for first-degree relatives (FDRs) is not yet well known. The aim of our study was to determine the incidence of both SP and/or CRC by studying the FDRs of our index SP cases and to propose an appropriate interval for colonoscopy surveillance in this group.

METHODS

From 2005 to December 2011, we prospectively included all patients from our hospital who fulfilled the SP diagnostic criteria. We interviewed FDRs face to face and offered a colonoscopy to those who were 35 years old or older. The study was carried out with conventional and high-definition colonoscopes and chromoendoscopy with indigo carmine at the discretion of a single endoscopist. The samples were assessed by two pathologists. We reviewed the clinical data for CRC diagnosed previously in FDRs.

RESULTS

From 2005, we collected all the new cases of SP and offered a colonoscopy to 95 FDRs of 34 pedigrees. We performed colonoscopies on 78 FDRs (82.1%). The incidence of SP in the FDRs was 32% (25 patients). Seventy-six percent of patients were diagnosed with SP as they had any number of serrated polyps proximal to the sigmoid colon. Only one patient was diagnosed with CRC as a result of the screening colonoscopy. 44.1% of our index cases had an FDR with a diagnosis of CRC.

CONCLUSION

Our series, which is the largest prospective cohort of FDRs published, reports an elevated incidence of SP in FDRs, thus supporting the need for screening colonoscopy in FDR and its inclusion in the guidelines.

Serrated Adenoma of Gastric Antrum: Alteration of Mucin Expression Profile and its Role in Carcinogenesis

Serrated adenomas usually occur in colon, the gastric localization is extremely rare. These polyps have their own carcinogenetic pathway with microsatellite instability. In this report, we present a serrated adenoma localized in gastric antrum with four control endoscopies and biopsies. Immunohistochemical panel of MUC1, MUC2, MUC5AC, and MUC6 was applied to the biopsies. Serrated component, MUC 2 expression increased but goblet cells and MUC5AC expression decreased in follow-up biopsies. This lesion probably was originated from a stem cell that had the potential of differentiation in gastric and intestinal way. This might result an incomplete metaplasia for both colon and stomach. Such lesions which originate from either colon or gastric mucosa may be precancerous and their carcinogenetic pathway may not represent its original organ.

RUNX3 inactivation in colorectal polyps arising through different pathways of colonic carcinogenesis

OBJECTIVES

We hypothesized that RUNX3 inactivation by promoter hypermethylation in colorectal polyps is an early molecular event in colorectal carcinogenesis.

METHODS

RUNX3 protein expression was analyzed immunohistochemically in 50 sporadic colorectal polyps comprising 19 hyperplastic polyps (HPs), 14 traditional serrated adenomas (TSAs), and 17 sporadic traditional adenomas (sTAs) as well as in 19 familial adenomatous polyposis (FAP) samples from 10 patients showing aberrant crypt foci (ACF) (n=91), small adenomas (SmAds) (n=40), and large adenomas (LAds) (n=13). In addition, we assessed the frequency of promoter hypermethylation of RUNX3 by methylation-specific PCR (MSP) in all the 50 sporadic polyps as well as 38 microdissected FAP polyps comprising ACF, SmAds, and LAds obtained from 7 FAP samples. A total of 12 normal colon samples were also included for RUNX3 MSP analysis.

RESULTS

Compared to normal colon (2 of 12, 16%) and sTAs (3 of 17, 18%), HPs (15 of 19, 79%) and TSAs (8 of 14, 57%) displayed significant inactivation of RUNX3 (P<0.05). In FAP, RUNX3 inactivation was more frequently seen in ACF (78 of 91, 86%), SmAds (25 of 40, 62%), and LAds (6 of 13, 46%) compared to normal mucosa (0 of 19, 0%) in the same samples (all P<0.05). Promoter hypermethylation of RUNX3 was significantly higher in colorectal polyps (64 of 87, 74%) compared to normal colon (2 of 12, 16%) (P=0.001). Serrated polyps such as HPs (17 of 19, 89%) and TSAs (12 of 14, 86%) were significantly more methylated than sTAs (7 of 17, 44%) (P=0.004). RUNX3 hypermethylation was observed in 28 of the total 38 (74%) FAP polyps. Overall, RUNX3 promoter methylation correlated with inactivation of RUNX3 expression in sporadic (27 of 36, 75%) (P=0.022) and FAP (21 of 28, 75%) (P=0.021) polyps.

CONCLUSIONS

Our data suggest that RUNX3 inactivation due to promoter hypermethylation in colorectal polyps represents an early event in colorectal cancer (CRC) progression. In addition, epigenetic RUNX3 inactivation is a frequent event in the serrated colonic polyps as well as in the ACF of FAP polyps.

Significance of serrated polyps of the colon

The fundamental view that colon adenocarcinomas arise only from conventional adenomas has been challenged by the now recognized hyperplastic polyp-serrated adenoma-adenocarcinoma pathway. This article describes the history of the serrated adenoma (both the traditional serrated adenoma and the sessile serrated adenoma) as well as the histology and endoscopic appearance of these lesions in comparison with hyperplastic polyps and mixed polyps. Although the exact pathway is the subject of ongoing research, compelling histologic associations and molecular phenotypes that define the model of the serrated polyp-carcinoma sequence, including microsatellite instability, BRAF/KRAS mutations, and CpG island methylator phenotype, provide strong evidence that this is a genuine pathway. Management of serrated neoplasia of the colon includes careful colonoscopy, complete removal of colonic polyps, sampling fields of diminutive polyps of the rectosigmoid, and basing surveillance on histology of removed polyps.

Cyclooxygenase-2 overexpression is common in serrated and non-serrated colorectal adenoma, but uncommon in hyperplastic polyp and sessile serrated polyp/adenoma

BACKGROUND

Cyclooxygenase-2 (COX-2, PTGS2) plays an important role in colorectal carcinogenesis. COX-2 overexpression in colorectal cancer is inversely associated with microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP). Evidence suggests that MSI/CIMP+ colorectal cancer may arise through the serrated tumorigenic pathway through various forms of serrated neoplasias. Therefore, we hypothesized that COX-2 may play a less important role in the serrated pathway.

METHODS

By immunohistochemistry, we assessed COX-2 expression in 24 hyperplastic polyps, 7 sessile serrated polyp/adenomas (SSA), 5 mixed polyps with SSA and adenoma, 27 traditional serrated adenomas, 515 non-serrated adenomas (tubular adenoma, tubulovillous adenoma and villous adenoma), 33 adenomas with intramucosal carcinomas, 96 adenocarcinomas with serration (corkscrew gland) and 111 adenocarcinomas without serration.

RESULTS

Strong (2+) COX-2 overexpression was more common in non-serrated adenomas (28% = 143/515) than in hyperplastic polyps (4.2% = 1/24, p = 0.008) and serrated polyps (7 SSAs and 5 mixed polyps) (0% = 0/12, p = 0.04). Furthermore, any (1+/2+) COX-2 overexpression was more frequent in non-serrated adenomas (60% = 307/515) than in hyperplastic polyps (13% = 3/24, p < 0.0001) and serrated polyps (SSAs and mixed polyps) (25% = 3/12, p = 0.03). Traditional serrated adenomas and non-serrated adenomas showed similar frequencies of COX-2 overexpression. Regardless of serration, COX-2 overexpression was frequent (approximately 85%) in colorectal adenocarcinomas. Tumor location was not significantly correlated with COX-2 overexpression, although there was a trend towards higher frequencies of COX-2 overexpression in distal tumors (than proximal tumors) among hyperplastic polyps, SSAs, mixed polyps, traditional serrated adenomas and adenocarcinomas.

CONCLUSION

COX-2 overexpression is infrequent in hyperplastic polyp, SSA and mixed polyp with SSA and adenoma, compared to non-serrated and serrated adenoma. COX-2 overexpression becomes more frequent as tumors progress to higher grade neoplasias. Our observations suggest that COX-2 may play a less significant role in the serrated pathway of tumorigenesis; however, COX-2 may still play a role in later stage of the serrated pathway.

Molecular classification and correlates in colorectal cancer

Molecular classification of colorectal cancer is evolving. As our understanding of colorectal carcinogenesis improves, we are incorporating new knowledge into the classification system. In particular, global genomic status [microsatellite instability (MSI) status and chromosomal instability (CIN) status] and epigenomic status [CpG island methylator phenotype (CIMP) status] play a significant role in determining clinical, pathological and biological characteristics of colorectal cancer. In this review, we discuss molecular classification and molecular correlates based on MSI status and CIMP status in colorectal cancer. Studying molecular correlates is important in cancer research because it can 1) provide clues to pathogenesis, 2) propose or support the existence of a new molecular subtype, 3) alert investigators to be aware of potential confounding factors in association studies, and 4) suggest surrogate markers in clinical or research settings.

Serrated polyps of the colorectum: is sessile serrated adenoma distinguishable from hyperplastic polyp in a daily practice?

The distinction between serrated polyps of the colon is complex, particularly between hyperplastic polyps (HP) and sessile serrated adenomas (SSA). Recent data show that SSA might be the precursors of serrated colonic cancers, underlining the necessity of identifying them. We characterized the demographic and pathologic characteristics of 102 serrated lesions among 321 polyps of the colorectum and determined if SSA can be microscopically distinguished from HP in biopsy material of a daily practice. There were 81 HP (79%) and 7 SSA (7%) of which one displayed low-grade dysplasia. Only six serrated polyps (6%) could not be correctly classified. The main architectural criteria for distinguishing SSA from HP is the serrated feature along the crypt axis and the rarity of undifferentiated cells in the lower third of the crypts. SSA was significantly more often located in the right colon and larger (median, 11 vs 4 mm) than HP. SSA are rare serrated polyps that can be distinguished from HP based on their morphology, location in the right colon, and larger size. One SSA of our series showed low-grade dysplasia supporting the concept that this lesion might be a precursor of serrated adenocarcinoma.

Carcinogenèse colorectale

Gene alterations which have been implicated in colorectal carcinogenesis are characterized by three major mechanisms: chromosomal instability, microsatellite instability, and epigenetic mechanisms (i.e., CpG island hypermethylation). Progress in understanding of these genetic and epigenetic instabilities has led to advances in the individualization and characterization of more homogeneous sub-groups of colorectal tumors with regard to progression, prognosis and response to therapy.

CpG island methylator phenotype (CIMP) of colorectal cancer is best characterised by quantitative DNA methylation analysis and prospective cohort studies

BACKGROUND

The concept of CpG island methylator phenotype (CIMP) is not universally accepted. Even if specific clinicopathological features have been associated with CIMP, investigators often failed to demonstrate a bimodal distribution of the number of methylated markers, which would suggest CIMP as a distinct subtype of colorectal cancer. Previous studies primarily used methylation specific polymerase chain reaction which might detect biologically insignificant low levels of methylation.

AIM

To demonstrate a distinct genetic profile of CIMP colorectal cancer using quantitative DNA methylation analysis that can distinguish high from low levels of DNA methylation.

MATERIALS AND METHODS

We developed quantitative real time polymerase chain reaction (MethyLight) assays and measured DNA methylation (percentage of methylated reference) of five carefully selected loci (promoters of CACNA1G, CDKN2A (p16), CRABP1, MLH1, and NEUROG1) in 460 colorectal cancers from large prospective cohorts.

RESULTS

There was a clear bimodal distribution of 80 microsatellite instability-high (MSI-H) tumours according to the number of methylated promoters, with no tumours showing 3/5 methylated loci. Thus we defined CIMP as having >or=4/5 methylated loci, and 17% (78) of the 460 tumours were classified as CIMP. CIMP was significantly associated with female sex, MSI, BRAF mutations, and wild-type KRAS. Both CIMP MSI-H tumours and CIMP microsatellite stable (MSS) tumours showed much higher frequencies of BRAF mutations (63% and 54%) than non-CIMP counterparts (non-CIMP MSI-H (0%, p<10(-5)) and non-CIMP MSS tumours (6.6%, p<10(-4)), respectively).

CONCLUSION

CIMP is best characterised by quantitative DNA methylation analysis. CIMP is a distinct epigenotype of colorectal cancer and may be less frequent than previously reported.

Phenotype of microsatellite-stable colorectal carcinomas with CpG island methylation

A distinctive pathway of colorectal carcinogenesis termed CpG island methylator phenotype is characterized by extensive DNA methylation in colorectal carcinoma (CRC) cells but not in nonneoplastic mucosa. Many CRCs with CpG island methylator phenotype have methylation of the hMLH1 mismatch repair gene and consequently have high levels of microsatellite instability (MSI-H). MSI-H confers distinctive clinical-pathologic features, but the phenotype of microsatellite-stable CRC with methylation has not been characterized in detail. We therefore examined the clinical-pathologic features of 87 sporadic microsatellite-stable CRCs that had been characterized for methylation of p16, p14, MGMT, hMLH1, MINT1, MINT2, and MINT31. Regression analyses of each clinical-pathologic characteristic were run against the individual and aggregated methylation markers to evaluate and quantify associations. CpG island methylation was associated with right-sided carcinoma (odds ratio = 6.9, P = 0.03). Paucity of gland formation, indicating poor differentiation, was strongly associated with methylation (beta = -42.6, P = 0.0008), as were presence of cribriform glands (beta = 34.3, P = 0.02) and lack of corkscrew/serrated glandular pattern (beta = -32.5, P = 0.03). Our epigenotype-phenotype correlation study shows that microsatellite-stable CRC with CpG island methylation have a distinctive pathologic phenotype with both similarities to and differences from MSI-H tumors.

Hyperplastic polyps and serrated adenomas: colonoscopic surveillance?

Hyperplastic polyps are not thought to carry a malignant potential. They are, therefore, not regularly screened by the majority of clinicians. We present two case reports of serrated adenomas that add to a small but expanding body of clinical and histological evidence that suggests a hyperplastic to neoplastic pathway. Regular colonoscopic surveillance may be indicated in at least some cases of hyperplastic polyposis

Management of Portuguese patients with hyperplastic polyposis and screening of at-risk first-degree relatives: a contribution for future guidelines based on a clinical study

BACKGROUND

Hyperplastic polyposis (HP) is a rare condition characterized by the presence of multiple hyperplastic polyps in the colon, which has been associated to an increased risk of colorectal cancer (CRC). Guidelines for management of this disease remain, so far, undefined.

AIMS

To evaluate, in symptomatic patients with HP, phenotypic characteristics as well as results of a screening program in their at-risk first-degree relatives.

PATIENTS

Pedigree information and clinical and endoscopic data of 14 patients with HP was studied. SEVENTEEN AND METHODS: at-risk first-degree relatives from six families were also invited to perform screening colonoscopy.

RESULTS

Twelve of fourteen (86%) patients had fewer than 100 colorectal polyps. Polyps' sizes ranged from 2 to 25 mm and were uniformly distributed through the whole colon in 43% of the patients. Hyperplastic polyps predominated, but 11/14 (79%) patients also harbored serrated as well as classic adenomatous polyps. CRC was present in 6/14 (43%) of the patients at the time of diagnosis. Familial history of CRC/polyps was positive in 6/12 (50%) of cases. Colonoscopy in at-risk relatives disclosed polyps in 10/17 (59%) of cases with at least one additional patient having criteria for HP.

CONCLUSIONS

Although small, this series demonstrates that a high level of suspicion is needed to diagnose the HP syndrome, in which serrated adenomas seem to be the hallmark. Although an elevated percentage of CRC was observed in this series of symptomatic patients with HP, prospective studies in asymptomatic individuals are needed to clearly quantify the risk of CRC in patients with HP. Because familial aggregation of HP was present in 3/12 (25%) of kindreds, screening colonoscopy should be offered to first-degree relatives.

Hyperplastic (serrated) polyps of the colorectum: relationship of CpG island methylator phenotype and K-ras mutation to location and histologic subtype

We investigated the frequency of promoter region CpG island methylation (CIM) of hMLH1, MGMT, MINT1, MINT2, and p16 and K-ras mutations in a total of 79 hyperplastic (serrated) polyps (HPs) from 75 patients and correlated the molecular profiles to polyp location in the colorectum, histologic variation, and other factors. Methylation-specific PCR (MS-PCR) was used to assay CIM status. HPs that showed CIM of one or more or two or more of the genes assayed were classified as CpG island methylator phenotype (CIMP) and CIMP-high (CIMP-H), respectively. PCR restriction fragment length polymorphism was used to assay K-ras codon 12 and 13 mutations. Logistic regression indicated a statistically significant trend for increasing odds for CIMP (P = 0.002) and CIMP-H (P < 0.001) according to proximity to the cecum or distance from the rectum. Conversely, K-ras codon 12 mutation was present in 13 of 40 (32.5%) distally located HPs compared with 2 of 39 (5.1%) proximal HPs (P = 0.006). Histologic subtype distribution varied by proximal and distal locations. Frequency of CIMP in serrated polyps with abnormal proliferation (SPAPs), differed significantly from goblet cell serrated polyps (GCSPs) (24 of 26, 92.3% vs. 6 of 13, 46.2%) (P = 0.003) and microvesicular serrated polyps (MVSPs) (26 of 38, 68.4%) (P = 0.03). Frequency of K-ras mutation in GCSPs (7 of 13, 54%) differed from that of MVSPs (6 of 38, 16%) (P = 0.01) and SPAPs (2 of 26, 8%) (P = 0.003). Location in the colorectum and histologic subtype were major determinants of the molecular profile of HPs. The molecular findings of CIMP and K-ras mutations appear to encompass most if not all HPs; CIMP profiles suggest that SPAP is the most advanced morphologic variant. We postulate that MVSP and GCSP may be precursor lesions that, if proximally located or larger, can progress to SPAP. Frequent K-ras mutations and infrequent CIMP distinguish the distal GCSP variant.