The significance of beta-catenin, E-cadherin, and P-cadherin expressions in neoplastic progression of colorectal mucosa: an immunohistochemical study

BACKGROUND AND STUDY AIMS: The purpose of the current study was to investigate the role of beta-catenin, E-cadherin and P-cadherin in colorectal carcinogenesis using tissue array method. PATIENTS AND METHODS: Core tissue biopsies were taken from paraffin-embedded tissue blocks of 167 cases including 26 normal mucosae (NM), 99 colorectal polyps (10 hyperplastic polyps (HP), 8 traditional serrated (TSA), 17 tubular (TA), 37 tubulovillous (TVA), and 27 villous adenomas (VA)), 14 adenomas with intramucosal carcinoma (ACA), and 28 colorectal cancers (CCA). Immunohistochemistry was performed using antibodies to beta-catenin, E-cadherin, and P-cadherin. Distribution of positivity was assessed using percentage expression while an arbitrary grading scale was used for staining intensity. RESULTS: beta-catenin expression was cytoplasmic, membranous, and nuclear. Both E-cadherin and P-cadherin expressions were confined to cytoplasmic-membranous compartments. Membranous expression of beta-catenin significantly decreased in CCA (p < 0.01). Nuclear beta-catenin expression significantly increased in close correlation with neoplastic sequence reaching its highest expression in ACA and CCA (p < 0.001). Polyps with intraepithelial neoplasia (IEN) showed significantly higher nuclear beta-catenin expression in parallel with increasing grades of IEN (p < 0.001). E-cadherin and P-cadherin expression increased in polyps, whereas a significant decrease in their expression was observed in CCA (p < 0.001) while E-cadherin expression significantly increased in CCA compared to NM (p < 0.001), no such difference was observed in P-cadherin expression. CONCLUSIONS: Nuclear beta-catenin expression correlating with the grade of IEN in polyps and carcinomas supports its role in colorectal carcinogenesis. E-cadherin and P-cadherin expressions in adenomas suggest that these molecules might have role in adenoma formation though not necessarily be involved in neoplastic progression.     

Emerging concepts in colorectal serrated polyps

Colorectal serrated polyps are heterogeneous epithelial lesions characterized by a serrated architecture. They include the classical hyperplastic polyps and the much rarer serrated adenomas and mixed polyps. Whereas serrated adenomas are composed of an unequivocal adenomatous epithelium with architectural serrated, mixed polyps include two separate hyperplastic and adenomatous components. During the past few years, another type of serrated polyp with only very subtle proliferation abnormalities has been described. These atypical serrated polyps may occur either sporadically or in the context of colorectal polyposis. Despite their close resemblance to traditional hyperplastic polyps, some authors argued that they should be regarded as authentically neoplastic lesions and have proposed to call them "sessile serrated adenomas". Their malignant potential requires their removal when discovered during colonoscopy. This article reviews the histological features, the endoscopic appearance, the natural history and the molecular phenotype of the different categories of serrated polyps and introduces the concept of "serrated neoplastic pathway" in the development of colorectal cancer.     

Cyclooxygenase-2 is overexpressed in serrated adenoma of the colorectum

PURPOSE: The aim of this study was to clarify whether cyclooxygenase-2 and cyclooxygenase-1 is expressed in hyperplastic polyps and serrated adenomas. METHODS: Forty-nine serrated adenomas and 25 hyperplastic polyps were immunostained using anticyclooxygenase-2 and anticyclooxygenase-1 antibodies. Cyclooxygenase-2 and cyclooxygenase-1 expression was investigated in all specimens. RESULTS: Cyclooxygenase-2 was expressed in dysplastic glands in the majority of serrated adenomas. Thirty-five of 49 (71.4 percent) serrated adenomas exhibited moderate to intense cyclooxygenase-2 immunoreactivity, and 8 of 25 hyperplastic polyps (32 percent) showed weak to moderate cyclooxygenase-2 immunoreactivity. Cyclooxygenase-1 immunoreactivity was very weak in all the hyperplastic polyps and serrated adenomas. CONCLUSIONS: These results suggest that cyclooxygenase-2 is overexpressed in serrated adenoma of the colorectum. Cyclooxygenase-2 inhibitors will reduce the incidence of serrated adenomas.     

Mixed colorectal polyps. An immunohistologic and mucin-histochemical study

The morphology of mixed colorectal polyps was analysed. Thirteen such polyps were found out of 2700 colorectal polyps (0.5%). Histology showed a spectrum of hyperplastic crypts from almost pure goblet cell population (two polyps) to hypermature serrated epithelium with scanty goblet cells (seven polyps). Tubular adenomas occurred in 12 polyps, and a tubulovillous adenoma was found in the largest polyp. Moderate dysplasia was seen in the five large polyps. The border between neoplastic and hyperplastic cells was usually sharp. Mucin histochemistry showed similarities between the mixed polyps and colorectal carcinomas--namely, the reduction/absence of sialomucin in both mature hyperplastic crypts and adenomatous glands. The expression of carcinoembryonic antigen within the hyperplastic crypts and within the neoplastic crypts showing moderate dysplasia was similar to that seen in colorectal carcinomas, whereas it was normal within the neoplastic crypts with low-grade dysplasia. IgA was reduced or absent in both components. Blood group antigen was found only within the adenomatous component of the largest polyp showing also moderate dysplasia.     

Expression of Cytokeratins 7 and 20 in Serrated Adenoma and Related Diseases

The entity of serrated adenoma of the colorectum was first proposed in 1990, and it was characterized as epithelial neoplasia combining the architectural features of a hyperplastic polyp with the cytological features of an adenoma. Over the past few years, various clinicopathological studies on serrated adenoma have been reported, but its histogenesis remains unclear. Recently the existence of a “serrated neoplasia pathway” leading to malignancy, which is different from the so-called adenoma–carcinoma sequence, has been discussed. Yao et al. reported that hyperplastic polyps and serrated adenomas share a common cell lineage with gastric differentiation. To clarify the existence of the serrated neoplasia pathway, we performed immunohistochemical staining of cytokeratin 7 (CK7) and cytokeratin 20 (CK20), which are commonly used to determine the primary site of a metastatic lesion, and we examined the pattern of CK7/CK20 expression in various colorectal lesions including 44 serrated adenomas, 25 hyperplastic polyps, 20 traditional adenomas, and 48 carcinomas. An obvious difference existed in the pattern of CK7/CK20 expression between the serrated lesions (hyperplastic polyps and serrated adenomas) and others. The majority of serrated adenomas and hyperplastic polyps presented a CK7+/CK20+ pattern, whereas most conventional adenomas and adenocarcinomas expressed CK7−/CK20+. Adenocarcinoma developing in serrated adenoma also presented a CK7+/CK20+ pattern. There are several reports that CK7 is a possible marker of transient dedifferentiation in the gastric carcinogenesis process. Taken together with the present results, a distinct pathway of colorectal carcinogenesis must exist, which is different from the adenoma–carcinoma sequence. CK7 is a possible marker for the serrated neoplasia pathway of colorectal carcinogenesis.     

Molecular characteristics of serrated adenomas of the colorectum

BACKGROUND: Serrated adenomas (SAs) of the colorectum combine architectural features of hyperplastic polyps and cytological features of classical adenomas. Molecular studies comparing SAs and classical adenomas suggest that each may be a distinct entity; in particular, it has been proposed that microsatellite instability (MSI) distinguishes SAs from classical adenomas and that SAs and the colorectal cancers arising from them develop along a pathway driven by low level microsatellite instability (MSI-L). AIMS: To define the molecular characteristics of SAs of the colorectum. MATERIALS AND METHODS: We analysed 39 SAs from 27 patients, including eight SAs from patients with familial adenomatous polyposis (FAP). We screened these polyps for selected molecular changes, including loss of heterozygosity (LOH) close to APC (5q21) and CRAC1 (15q13-q22), MSI, and mutations of K-ras, APC, p53, and beta-catenin. Expression patterns of beta-catenin, p53, MLH1, MSH2, E-cadherin, and O(6)-methylguanine DNA methyltransferase (MGMT) were assessed by immunohistochemistry. Comparative genomic hybridisation was performed on several polyps. RESULTS: MSI was rare (<5% cases) and there was no loss of expression of mismatch repair proteins. Wnt pathway abnormalities (APC mutation/LOH, beta-catenin mutation/nuclear expression) occurred in 11 SAs, including 6/31 (19%) non-FAP tumours. CRAC1 LOH occurred in 23% of tumours. K-ras mutations and p53 mutations/overexpression were found in 15% and 8% of SAs, respectively. Loss of MGMT expression occurred in 18% of polyps and showed a borderline association with K-ras mutations. Aberrant E-cadherin expression was found in seven polyps. Comparative genomic hybridisation detected no gains or deletions of chromosomal material. CONCLUSIONS: The serrated pathway of colorectal tumorigenesis appears to be heterogeneous. In common with classical adenomas, some SAs develop along pathways involving changes in APC/beta-catenin. SAs rarely show MSI or any evidence of chromosomal-scale genetic instability. K-ras mutations may however be less common in SAs than in classical adenomas. Some SAs may harbour changes in the CRAC1 gene. Changes in known genes do not account for the growth of the majority of SAs.     

Two cases of inverted hyperplastic polyps of the colon and association with adenoma

Here we report two cases of inverted hyperplastic polyps of the colon. The first patient showed three inverted hyperplastic polyps in the ascending colon, one of which was associated with adenoma. We immunostained this adenoma-associated polyp using anti-beta-catenin antibody and found accumulation of beta-catenin in the cytoplasm of the adenomatous lesion but not in the inverted hyperplastic polyp. This suggested an adenomatous polyposis coli (APC) mutation in the adenomatous region but not in the inverted hyperplastic polyp. The inverted hyperplastic polyp in the second patient was located at the caecum and was studied using magnifying colonoscopy. The polyp appeared to be flat and elevated with a depressed pit in the centre. After spraying with methylene blue dye, the pit pattern of the lesion was observed and small asteroid pits on the polyp were found, consistent with a hyperplastic gland pattern. From these results, we diagnosed inverted hyperplastic polyp of the colon by colonoscopy.     

High prevalence of sessile serrated adenomas with BRAF mutations: a prospective study of patients undergoing colonoscopy

BACKGROUND & AIMS: Sporadic colorectal cancers with a high degree of microsatellite instability are a clinically distinct subgroup with a high incidence of BRAF mutation and are widely considered to develop from serrated polyps. Previous studies of serrated polyps have been highly selected and largely retrospective. This prospective study examined the prevalence of sessile serrated adenomas and determined the incidence of BRAF and K-ras mutations in different types of polyps. METHODS: An unselected consecutive series of 190 patients underwent magnifying chromoendoscopy. Polyp location, size, and histologic classification were recorded. All polyps were screened for BRAF V600E and K-ras codon 12 and 13 mutations. RESULTS: Polyps were detected in 72% of patients. Most (60%) were adenomas (tubular adenomas, tubulovillous adenomas), followed by hyperplastic polyps (29%), sessile serrated adenomas (SSAs; 9%), traditional serrated adenomas (0.7%), and mixed polyps (1.7%). Adenomas were more prevalent in the proximal colon (73%), as were SSAs (75%), which tended to be large (64% >5 mm). The presence of at least one SSA was associated with increased polyp burden (5.0 vs 2.5; P < .0001) and female sex (P < .05). BRAF mutation was rare in adenomas (1/248 [0.4%]) but common in SSAs (78%), traditional serrated adenomas (66%), mixed polyps (57%), and microvesicular hyperplastic polyps (70%). K-ras mutations were significantly associated with goblet cell hyperplastic polyps and tubulovillous adenomas (P < .001). CONCLUSIONS: The prevalence of SSAs is approximately 9% in patients undergoing colonoscopy. They are associated with BRAF mutation, proximal location, female sex, and presence of multiple polyps. These findings emphasize the importance of identifying and removing these lesions for endoscopic prevention of colorectal cancer.     

p53 overexpression in flat serrated adenomas and flat tubular adenomas of the colorectal mucosa

The expression of the p53 protein was investigated in flat serrated neoplasias as well as in other histological phenotypes of flat or exophytic hyperplasias or neoplasias of the colorectal, mucosa. A total of 104 such lesions were analyzed: 24 were flat serrated neoplasias (22 flat serrated adenomas and 2 flat serrated adenocarcinomas), 26 flat tubular adenomas, 17 flat hyperplastic polyps, 29 exophytic tubular and/or villous neoplasias (23 adenomas and 6 exophytic adenocarcinomas) and the remaining 8, exophytic hyperplastic polyps. Deparaffinized, rehydrated sections were treated immunohistochemically to detect those overexpressing the p53 protein. Lesions having slight (+), moderate (++) or intense (+++) staining were considered immunoreactive. The results showed that 50% of the flat serrated adenomas with low-grade dysplasia (LGD) and 66.7% of those with high-grade dysplasia (HGD) had p53 immunoreactivity. None of the flat tubular or of the exophytic adenomas with LGD expressed p53, but immunoreactivity was present in 61.5% of the flat tubular adenomas with HGD and in 52.3% of the exophytic adenomas with HGD. All adenocarcinomas had an intense p53 reaction. Weak p53 expression was demonstrated by 11.7% of the flat hyperplastic polyps but none of the exophytic polyps reacted. The occurrence of p53 expression in flat serrated adenomas with LGD suggested that, despite its low histological profile, one-half of those lesions could be biologically already committed to independent growth. The occurrence of p53 expression in nearly 12% of the flat hyperplastic polyps was totally unexpected and deserves further investigation. Flat serrated adenoma emerges as a novel, independent histological entity among the various phenotypes of flat neoplasias of the colorectal mucosa.     

Endoscopic and histologic characteristics of serrated lesions

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

Phenotypic characteristics and risk of cancer development in hyperplastic polyposis: case series and literature review

OBJECTIVES: Hyperplastic polyposis (HP) is a poorly understood condition. The aim of this study is to describe the phenotype and the risk of cancer in HP. METHODS: Patients with HP, as defined by the WHO International Classification, were identified through the University of Utah and the Huntsman Cancer Institute databases. Family history was retrieved when possible. RESULTS: Fifteen patients were identified (10 M, 5 F) with a mean age at diagnosis of 52.6 +/- 16.4 yr (18-71). Sixty-five colonoscopies were performed (2-11 per person). A median of 90 polyps (16-210) per person and 15 polyps (range, 0-100) per procedure were reported. The median follow-up was 33 months (3-133); no cancer occurred during this period. Polyps were more frequent in the distal than the proximal colon (74%vs 26%; p < 0.001). The median polyp size was 4 mm (1-40 mm). Fifty-one hyperplastic polyps >10 mm were identified in 10 patients (38 proximal, 13 distal; p= 0.089). Forty-eight adenomas were found in 11 patients and were uniformly distributed. Serrated adenomas (n = 3) were found in one patient. A unique patient had 20 large hyperplastic polyps, 24 adenomas, 3 serrated adenomas, and 118 hyperplastic polyps. None of the patients had a first-degree relative with colon cancer. CONCLUSIONS: In HP, hyperplastic polyps are more frequently distal colonic, and vary greatly in size and number. Most patients also develop adenomas that are distributed throughout the colon. No cancers developed within 3 yr of follow-up. Colonoscopic surveillance at intervals of 1-3 yr, depending upon the number and size of both adenomatous and hyperplastic polyps, appears prudent.     

Emerging concepts in colorectal neoplasia

An understanding of the mechanisms that explain the initiation and early evolution of colorectal cancer should facilitate the development of new approaches to effective prevention and intervention. This review highlights deficiencies in the current model for colorectal neoplasia in which APC mutation is placed at the point of initiation. Other genes implicated in the regulation of apoptosis and DNA repair may underlie the early development of colorectal cancer. Inactivation of these genes may occur not by mutation or loss but through silencing mediated by methylation of the gene's promoter region. hMLH1 and MGMT are examples of DNA repair genes that are silenced by methylation. Loss of expression of hMLH1 and MGMT protein has been demonstrated immunohistochemically in serrated polyps. Multiple lines of evidence point to a "serrated" pathway of neoplasia that is driven by inhibition of apoptosis and the subsequent inactivation of DNA repair genes by promoter methylation. The earliest lesions in this pathway are aberrant crypt foci (ACF). These may develop into hyperplastic polyps or transform while still of microscopic size into admixed polyps, serrated adenomas, or traditional adenomas. Cancers developing from these lesions may show high- or low-level microsatellite instability (MSI-H and MSI-L, respectively) or may be microsatellite stable (MSS). The suggested clinical model for this alternative pathway is the condition hyperplastic polyposis. If colorectal cancer is a heterogeneous disease comprising discrete subsets that evolve through different pathways, it is evident that these subsets will need to be studied individually in the future.     

Serrated adenoma in familial adenomatous polyposis: relation to germline APC gene mutation

BACKGROUND: Serrated adenoma is a precursor of colorectal cancer. AIM: To clarify possible genotype-phenotype correlations of serrated adenomas in familial adenomatous polyposis (FAP). Patients: Eleven patients from eight families with FAP. METHODS: We performed total colonoscopy with multiple biopsies in patients. Neoplasia with a serrated glandular structure was regarded as a serrated adenoma. In each patient, germline mutations of the APC gene were determined. Colonic phenotype was compared with germline mutations of the APC gene. RESULTS: Serrated adenomas were found in three patients. These patients had macroscopic polyps <100 in number. Pedigrees with serrated adenomas had the truncating germline APC mutation at codon 161, 332, or 1556 while in the other pedigrees mutations were found between codons 554 and 1324. CONCLUSIONS: In FAP, serrated adenoma may be a phenotype characteristic of the attenuated form.     

Pathophysiology, clinical presentation, and management of colon cancer

Colon cancer is believed to arise from two types of precursor polyps via two distinct pathways: conventional adenomas by the conventional adenoma-to-carcinoma sequence and serrated adenomas according to the serrated adenoma-to-carcinoma theory. Conventional adenomas arise from mutation of the APC gene; progression to colon cancer is a multistep process. The fundamental genetic defect in serrated adenomas is unknown. Environmental factors can increase the risk for colon cancer. Advanced colon cancer often presents with symptoms, but early colon cancer and premalignant adenomatous polyps commonly are asymptomatic, rendering them difficult to detect and providing the rationale for mass screening of adults over age 50.     

Reducing the incidence and mortality of colon cancer: mass screening and colonoscopic polypectomy

Most colon cancers arise from conventional adenomatous polyps (conventional adenoma-to-carcinoma sequence), while some colon cancers appear to arise from the recently recognized serrated adenomatous polyp (serrated adenoma-to-carcinoma theory). Because conventional adenomas and serrated adenomas are usually asymptomatic, mass screening of asymptomatic patients has become the cornerstone for detecting and eliminating these precursor lesions to reduce the risk of colon cancer. Colonoscopy has become the primary screening test because of its high sensitivity and specificity, and the ability to perform polypectomy. Other screening tests include guaiac tests or fecal immunochemical tests (FIT) for fecal occult blood, and flexible sigmoidoscopy. A minimal colonoscopic withdrawal time of 6 minutes is important to maximize polyp detection at colonoscopy. Chromoendoscopy is an experimental technique used to highlight abnormal colonic areas to identify neoplastic tissue and to potentially determine the histology of colonic polyps at colonoscopy based on superficial pit anatomy.     

Surveillance strategies in patients after polypectomy

Colorectal cancer (CRC) is a major cause of cancer death in the Western world. It develops slowly over several years from premalignant lesions (most prominently adenomatous polyps) to invasive cancer. The molecular basis of CRC pathogenesis has been well characterized. The most effective method to prevent CRC is endoscopic polypectomy. However, adenomatous polyps are known to recur at significant rates. The aim of surveillance programs after polypectomy is to further reduce the incidence of CRC in individuals where precancerous lesions have been identified and treated. However, the medical risks and the costs of repeated examinations must be kept as low as possible. Therefore, the identification of patient subgroups with a particular low cancer risk who may be followed-up less frequently seems important. There is recent evidence that other colorectal lesions, namely flat and depressed type adenomas (F&D adenoma) and possibly some hyperplastic polyps and serrated adenomas may also carry a malignant potential which could influence our screening, treatment and surveillance strategies for the colorectum in the future. General surveillance guidelines regarding these entities have not been issued to date. This article will first discuss the biology, natural history, present surveillance recommendations and future issues for sporadic adenomatous polyps. Then, recent literature on F&D type adenomas, hyperplastic polyps and serrated adenomas will be reviewed with respect to their malignant potential and the potential necessity for treatment and surveillance of these lesions.     

Mucin associated Tn and sialosyl-Tn antigen expression in colorectal polyps.

Sialosyl-Tn antigen and its immediate precursor, Tn antigen, are carbohydrate structures associated with the earliest steps of mucin O-linked glycosylation. Both antigens have been shown previously to be highly sensitive and specific markers of colorectal cancer. One hundred and three colorectal polyps (79 adenomatous; 24 hyperplastic) were examined for expression of Tn antigen using vicia villosa isolectin B4, and for sialosyl-Tn antigen by monoclonal antibody TKH2. Tn antigen was expressed by all of the polyps studied. Sialosyl-Tn, on the other hand was expressed weakly by a few cells in 7 of 24 (29%) hyperplastic polyps. Among the adenomatous polyps, 56% expressed sialosyl-Tn and expression correlated with larger adenoma size, greater villous component, and more severe grades of dysplasia. In individuals with two or more synchronous adenomas, the level of sialosyl-Tn expression within an adenoma was associated with the severity of cytological atypia. All the adenomas that contained a focus of invasive carcinoma expressed sialosyl-Tn. These results indicate that colorectal polyps manifest incomplete glycosylation, exposing antigens in the innermost region of mucin oligosaccharides. In addition, the correlation of sialosyl-Tn antigen expression with the adenoma-carcinoma sequence may make this a useful marker for studying malignant progression in the colon.     

Hyperplastic polyps of the colorectum—Innocent or guilty?

Hyperplastic polyps have traditionally been regarded as nonneoplastic polyps lacking malignant potential. The demonstration of genetic alterations within these lesions indicates an underlying neoplastic cause. There is evidence that hyperplastic polyps are heterogeneous. Most are innocuous, but subsets may have malignant potential. Risk factors for neoplastic progression include multiple, large, and proximally located polyps. Aberrant methylation resulting in the silencing of cancer genes may be an important underlying mechanism, particularly in pathways progessing to tumors with DNA microsatellite instability. Lesions intermediate between hyperplastic polyp and cancer include admixed polyps and serrated adenomas. Currently, pathologists have different thresholds for diagnosing serrated adenomas, including the distinction from large hyperplastic polyps. Reasons for over looking this pathway in the past may include rapid tumor progression and the fact that proximally located hyperplastic polyps may be flat and not especially numerous. Management of the serrated pathway of colorectal neoplasia may require novel approaches to screening, early detection, and prevention.     

Serrated neoplasia of the colorectum

Serrated polyps of the colorectum form a group of related lesions which include aberrant crypt foci （ACF）, conventional hyperplastic polyps, mixed （admixed） polyps, serrated adenomas and sessile serrated adenomas. In recent years the molecular differences between these morphologically similar lesions have been highlighted, and their differing biological potential has been realised. In particular, the sessile serrated adenoma has become recognised as the precursor lesion to a group of sporadic colorectal carcinomas characterised by morphological and molecular features distinct from conventional adenomas. These recent findings have challenged the long held paradigm that all colorectal carcinomas arise via the traditional adenoma-carcinoma sequence. In addition, they present a major challenge for the early detection and management of colorectal cancer, which is no longer regarded as a homogeneous entity.