Microvesicular Hyperplastic Polyps Research Articles

Endoscopic characteristics to differentiate sessile serrated lesion and microvesicular hyperplastic polyp from goblet cell-rich hyperplastic polyp

Backgrounds Among colorectal serrated polyps (SPs), sessile serrated lesions (SSLs) and hyperplastic polyps (HPs) show a similar endoscopic appearance. However, the endoscopic distinctions between the two categories, microvesicular HP (MVHP) and goblet cell-rich HP (GCHP) are not well understood. Therefore, we compared the endoscopic features of SSL, MVHP, and GCHP. Methods This retrospective, cross-sectional study was conducted at the Toyoshima Endoscopy Clinic. We examined the polyp size, location, Paris classification type, mucus cap, indistinct border, expanded crypt opening, varicose microvascular vessels, and JNET classification type. Multivariable analysis of each endoscopic finding using a binomial logistic regression model determined the factors that predicted SP histology. Results A total of 670 SPs were enrolled in this study, comprising 159 SSLs, 361 MVHPs, and 150 GCHPs. On comparing the SSL + MVHP group and GCHP, a mucus cap (partial regression coefficient 1.705), expanded crypt opening (1.828), and varicose microvascular vessels (1.270) were more often observed in SSL + MVHP group compared with GCHP. In the comparison between MVHP and GCHP, a mucus cap (1.564), expanded crypt opening (1.802), and varicose microvascular vessels (1.288) were more often found in MVHP in contrast to GCHP. When comparing SSL and MVHP, SSLs were more likely to be in the proximal colon (0.662) and were larger (0.198) than MVHPs. No significant differences were observed in other endoscopic findings. Conclusions SSL and MVHP have endoscopic appearances that differ from those of GCHP. Considering MVHP and GCHP as distinct entities may aid in the endoscopic diagnosis of SPs.

Increased GS-II lectin binding and SATB2 downregulation are biological features for sessile serrated lesions and microvesicular hyperplastic polyps.

Sessile serrated lesions (SSLs) and microvesicular hyperplastic polyps (MVHPs) are colorectal lesions displaying gastric differentiation. Griffonia simplicifolia-II (GS-II) is a lectin specific to terminal α/βGlcNAc residues. Here, we assessed GS-II binding and performed immunostaining for HIK1083 (specific to terminal αGlcNAc residues), MUC5AC, MUC6, and special AT-rich sequence binding protein 2 (SATB2) in SSLs, MVHPs, and tubular adenomas (TAs). We observed MUC5AC positivity in 28 of 30 SSLs, but in only three of 23 TAs. Moreover, 24 of 30 SSLs were MUC6-positive, while none of the 23 TAs were MUC6-positive. None of the 30 SSLs or 23 TAs showed HIK1083 positivity. All 30 SSLs and 26 MVHPs were GS-II-positive, while only seven of 23 were in TAs. GS-II staining was mainly distributed in the Golgi region, but SSLs and MVHPs showed goblet cell distribution, in 20 of 30 and 19 of 26 cases, respectively. All SSLs, MVHPs, and TAs were SATB2-positive, but 21 of 30 SSLs and 12 of 26 MVHPs showed decreased staining intensity relative to adjacent mucosa, a decrease seen in only two of 23 in TAs. These results indicate overall that increased terminal βGlcNAc and decreased SATB2 expression are characteristics of SSLs and MVHPs.

Increased Gs-Ii Lectin Binding and Satb2 Downregulation are Biological Features for Sessile Serrated Lesions and Microvesicular Hyperplastic Polyps

Increased Gs-Ii Lectin Binding and Satb2 Downregulation are Biological Features for Sessile Serrated Lesions and Microvesicular Hyperplastic Polyps

Significance of gene mutations in the Wnt signaling pathway in traditional serrated adenomas of the colon and rectum.

Recent studies have shown that colorectal serrated lesions, which include sessile serrated adenomas (SSAs) and traditional serrated adenomas (TSAs), are precursors of colorectal cancer. However, the molecular mechanisms underlying the carcinogenesis, particularly in TSAs, remain largely uncharacterized. To clarify their molecular and clinicopathological characteristics, we performed mutation and methylation analyses of cancer-associated genes in 78 serrated lesions, including TSAs, SSAs and microvesicular hyperplastic polyps. Target exon sequence analysis was performed with 39 genes, including genes known to be frequently mutated in colorectal cancers and/or serrated lesions. We also used bisulfite pyrosequencing to assess the methylation status of various cancer-associated genes and marker genes of the CpG island methylator phenotype (CIMP). The prevalence of mutations in genes associated with Wnt signaling was significantly higher in TSAs than SSAs (65% vs. 28%, p < 0.01). Among those, RNF43 mutations were observed in 38% of TSAs and 17% of SSAs. In immunohistochemical studies of 39 serrated lesions, the prevalence of abnormal nuclear β-catenin accumulation was significantly higher in TSAs (57%) than SSAs (8%) (P = 0.01). SMOC1 methylation was detected in 54% of TSAs but in no SSAs (p < 0.01). Additionally, SMOC1 methylation was more prevalent among TSAs with KRAS mutation (82%) than with BRAF mutation (38%, p = 0.03). Lesions with CIMP-high or RNF43 mutations were detected only in TSAs with BRAF mutation, suggesting two distinct carcinogenic pathways in TSAs. Mutations in genes associated with Wnt signaling play a greater role in the carcinogenesis of TSAs than SSAs.

Macroscopic and microscopic morphology and molecular profiling to distinguish heterogeneous traditional serrated adenomas of the colorectum.

Serrated lesions of the colorectum often have complex histological morphology, and some groups include subtypes with different molecular biology. This study aimed to characterize serrated lesions with heterogeneous histology that was dominated by a traditional serrated adenoma (TSA) component. Representative lesions were selected based on both endoscopic and histological features. If a lesion had more than one component, each of the different structural parts was considered as a separate sample. DNA was extracted from 177 samples of 60 lesions and amplified to screen for BRAF and K/NRAS mutations. Heterogeneous TSA samples were classified into four categories: sessile serrated lesion with TSA (SA-1); TSAs with microvesicular hyperplastic polyp (SA-2); TSAs with unclassified adenoma, characterized by tubulo-serrated histology (SA-3); and TSAs with conventional adenomas (SA-4). On endoscopy, SA-1 lesions had sessile-elevated morphology with the small reddish elevations; SA-2 lesions had a pedunculated appearance with a whitish mucosal component at the stalk; SA-3 lesions had a sessile-elevated component surrounded by flat spreading margins; and SA-4 lesions had mixed adenomatous morphology. Eighteen of the 19 category SA-1 and -2 lesions (95%) had BRAF mutations, and all of the SA-3 and -4 lesions had K/NRAS mutations. Traditional serrated adenomas were classified into two phenotypes according to their molecular characteristics: microvesicular serrated subtypes with BRAF mutations (SA-1 and -2 lesions) and subtypes containing tubulo-serrated/conventional adenoma with K/NRAS mutations (SA-3 and -4 lesions). Each subtype had characteristic macroscopic and microscopic morphologies and was distinct on endoscopy.

Molecular Profiling Based on KRAS/BRAF Mutation, Methylation, and Microsatellite Statuses in Serrated Lesions

AimThe aim of your study is to characterize serrated lesions according to their molecular patterns, specifically BRAF/KRAS mutation, methylation, and microsatellite statuses. We evaluated the molecular patterns of 163 serrated lesions, including 37 microvesicular hyperplastic polyps, 73 sessile serrated adenomas/polyps (SSA/Ps), 31 traditional serrated adenomas, and 22 SSA/Ps with cytological dysplasia/adenocarcinoma.MethodsMutations in BRAF (V600E)/KRAS (exon 2) and microsatellite status [microsatellite stability (MSS) vs. MSI] were examined using a pyrosequencer and the PCR-based microsatellite method, respectively. DNA methylation status was classified as low (LME), intermediate (IME), or high methylation epigenotype (HME) according to a PCR-based two-step method. In addition, mucin and annexin A10 expression was examined. Finally, we performed a hierarchical clustering analysis of the BRAF/KRAS mutation, DNA methylation, and microsatellite statuses.ResultsThe molecular patterns observed in the serrated lesions could be divided into five subgroups: lesions characterized by (1) BRAF mutation, HME, and MSI; (2) BRAF mutation, HME, and MSS; (3) BRAF mutation, LME/IME, and MSS; (4) no BRAF/KRAS mutations, LME/IME, and MSS; and (5) KRAS mutation, LME/IME, and MSS. In addition, we demonstrated that these observed molecular patterns help identify the associations of the molecular patterns and markers (i.e., mucin and annexin A10) with the clinicopathological findings, including histological features and histological diagnosis.ConclusionsWe suggest that the identified molecular patterns play an important role in the pathway of serrated lesion development.

Colonic perineurioma (benign fibroblastic polyp): case report and review of the literature

BackgroundColorectal perineuriomas are uncommon benign mucosal-based proliferations of mesenchymal cells that express perineurial markers, often associated with colonic crypts displaying a serrated/hyperplastic architecture. The vast majority of cases arise distal to the splenic flexure and have been described as sessile polyps. Using molecular analysis, BRAF mutations have been demonstrated in the serrated crypt epithelium. We report a new case of perineurioma presenting as a pedunculated polyp in the transverse colon, with prominent hemosiderin deposits in the uninvolved lamina propria that separated the perineurial proliferation from the surface epithelium, a previously unreported histological finding. By using immunohistochemistry, we demonstrated the presence of BRAF V600E mutated protein in the serrated crypt epithelium. In addition, a review of the literature on colorectal perineurioma is provided.Case presentationA 5 mm pedunculated polyp was removed from the transverse colon of a 42 year old man who presented with epigastric pain, weight loss and rectal bleeding. A proliferation of uniform plump spindled cells expanded the lamina propria and separated serrated colonic crypts. The epithelial component closely resembled microvesicular hyperplastic polyp. Immunohistochemical stains for epithelial membrane antigen (EMA), glucose transporter 1 (GLUT1) and collagen IV were positive in the stromal proliferation. A mutation-specific monoclonal antibody directed against BRAF V600E showed positive cytoplasmic staining in the serrated crypt epithelium but not in the perineurial proliferation. Conspicuous hemosiderin deposition was seen in the inflamed lamina propria between the perineurial proliferation and the surface epithelium.ConclusionAlthough the majority of colorectal perineuriomas occur in the sigmoid colon and rectum and are described as sessile polyps, colorectal perineurioma can present as a pedunculated polyp proximal to the splenic flexure as described in this case. Conspicuous hemosiderin deposition can be seen in the superficial lamina propria. BRAF mutations are limited to the serrated crypt epithelium.

Expression of doublecortin and CaM kinase-like-1 protein in serrated neoplasia of the colorectum.

The adenoma-carcinoma sequence (ACS) and the serrated pathway are two distinct developmental routes leading to the formation of colorectal carcinoma. Recently, the doublecortin and CaM kinase-like-1 protein (DCLK1) has been reported to serve as an intestinal cancer stem cell marker and has been demonstrated to be overexpressed through the ACS; however, there is a lack of reports on the role of DCLK1 in the serrated pathway. To clarify the correlation between DCLK1 protein expression and clinicopathological characteristics of the serrated tumorigenic pathway, the present study used immunohistochemistry to examine the expression of DCLK1 in endoscopically resected samples of 62 serrated polyps [20 hyperplastic polyps (HPs), 16 traditional serrated adenomas (TSAs) and 26 sessile serrated adenoma-polyps (SSA/Ps)], as well as 20 non-serrated adenomas, 20 carcinoma in adenomas (CIAs) and 18 early pure colorectal carcinomas without any adenoma component (EPCs). Based on immunostaining score, high DCLK1 expression was detected in 20.0% of HPs (23.1% of microvesicular HPs and 14.3% of goblet cell HPs), 37.5% of TSAs, 7.7% of SSA/Ps, 80.0% of non-serrated adenomas, 75.0% of CIAs and 50.0% of EPCs. Negative or low DCLK1 expression was frequently observed in TSAs (P<0.005), SSA/Ps (P<0.00001) and EPCs (P<0.04) compared with non-serrated adenomas and CIAs. In addition, negative or low DCLK1 expression was significantly more frequent in SSA/Ps (92.3%) compared with TSAs (62.5%; P<0.05). Thus, the expression pattern of DCLK1 between the serrated pathway and ACS differed, indicating that DCLK1 expression may perform a secondary role in serrated tumorigenesis. In addition, the data indicates that EPCs may contain tumors derived from the serrated pathway as well as the ACS.

Abstract IA05: The serrated pathway of colorectal tumorigenesis

Abstract IA05: The serrated pathway of colorectal tumorigenesis

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

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

Comparison of sessile serrated adenoma (SSA) histopathologic diagnostic criteria and their effect on reclassification rate of microvesicular hyperplastic polyps to SSA

Comparison of sessile serrated adenoma (SSA) histopathologic diagnostic criteria and their effect on reclassification rate of microvesicular hyperplastic polyps to SSA

Traditional serrated adenoma: an update.

Although recognized 25 years ago, the traditional serrated adenoma (TSA) remains an ongoing source of diagnostic and biologic debate. Recent research has greatly improved our understanding of the morphological and molecular aspects of these polyps. In particular, the recognition of ectopic crypt foci (ECFs) in combination with typical cytology and slitlike serrations improves diagnostic reproducibility. Awareness that many TSAs, particularly BRAF-mutated TSAs, arise in precursor microvesicular hyperplastic polyps and sessile serrated adenomas can aid in making this diagnosis and should not be confused with a sessile serrated adenoma with dysplasia. At a molecular level, TSAs can be divided into 2 groups based on their BRAF or KRAS mutation status. The development of overt cytologic dysplasia is accompanied by TP53 mutation, Wnt pathway activation, and, in some cases, silencing of CDKN2A. Importantly, however, mismatch repair enzyme function is retained. Thus, the TSA is an important precursor of aggressive molecular subtypes of colorectal carcinoma.

A morphologic reappraisal of endoscopically but not histologically apparent polyps and the emergence of the overlooked goblet cell--rich hyperplastic polyp.

Goblet cell--rich hyperplastic polyps (GCRHP) are morphologically subtle compared to microvesicular hyperplastic polyps (MVHP) and are believed to be the most commonly unrecognized serrated polyp, though this has not been systematically studied. We hypothesize that a gastrointestinal pathologist's review of endoscopically but not histologically apparent polyps will identify previously missed GCRHPs, a finding that may be clinically significant if the addition of this subtype of serrated polyp contributes to sufficient numeric criteria for a clinical diagnosis of serrated polyposis syndrome (SPS). Two blinded reviews were performed on 160 endoscopically but not histologically apparent polyps by a gastrointestinal pathologist, separated by a 6 month "washout period." A final review diagnosis of GCRHP was applied to all polyps with complete agreement on both reviews. Patient records were then searched to determine if the addition of a GCRHP resulted in sufficient numeric criteria for a clinical diagnosis of SPS. Fourteen (9%) polyps were reclassified as GCRHPs. The majority (n = 12, 86%) were originally called "colonic mucosa with surface hyperplastic change (CMWSHC)." Two polyps (1%) were re-classified as MVHPs. No other serrated or adenomatous polyps were identified. For each patient, the addition of a hyperplastic polyp did not result in a clinical diagnosis of SPS, though one patient fell short of this diagnosis by only one polyp. GCRHPs are the most commonly underdiagnosed serrated polyp and are often called CMWSHC. The addition of previously missed GCRHPs is unlikely to contribute to a diagnosis of SPS in an individual patient.

Gastric-type expression signature in serrated pathway–associated colorectal tumors

Accumulating evidence has indicated that serrated pathway-associated colorectal tumors may be associated with aberrant gastric-type differentiation. Here, we investigated the immunoexpression profiles of gastric-type markers and intestinal-type markers in colorectal tumors, focusing on their relation to serrated pathway-associated tumors. Immunohistochemistry for 7 gastric-type markers (ANXA10, VSIG1, CLDN18, CTSE, TFF2, MUC5AC, and MUC6) and 2 intestinal-type markers (CDX2 and CK20) was performed in 36 normal gastric/colorectal mucosa tissues, 163 colorectal polyps, and 175 microsatellite-unstable colorectal carcinomas (MSI-H CRCs). In normal tissues, all 7 candidate gastric-type markers showed expressional specificity for normal gastric mucosa. Among the colorectal polyps, sessile serrated adenoma/polyps demonstrated the highest positive rate of ANXA10, CLDN18, MUC5AC, and MUC6 expression (87%, 35%, 61%, and 52%, respectively). Microvesicular hyperplastic polyps showed the highest frequencies of ANXA10, VSIG1, and TFF2 positivity (87%, 87%, and 67%, respectively). ANXA10 and MUC6 expression was not detected in all conventional adenomas. In MSI-H CRCs, the expression of ANXA10, TFF2, and MUC5AC was significantly associated with sporadic tumors (P < .001, P = .01, and P < .001, respectively). Moreover, all of the 7 gastric-type markers were significantly related to preferential expression in proximal colon carcinomas among MSI-H CRCs. CDX2 and CK20 expression was retained in all colorectal polyps, whereas there were significantly high frequencies of CDX2 loss (28%) and CK20 loss (29%) in sporadic tumors among MSI-H CRCs. In conclusion, the early gain of gastric differentiation and late loss of intestinal differentiation are immunophenotypic features in the serrated pathway to colorectal carcinoma.

Claudin-1 positive proliferations in serrated colorectal polyps

Aims To analyse the frequency of Claudin-1 positive proliferations in serrated colorectal polyps. Methods Consecutive colorectal polyps originally diagnosed as sessile serrated adenomas (SSAs) and large hyperplastic polyps were reviewed and reclassified as SSAs, microvesicular hyperplastic polyps (MVHP), or serrated polyps (SP) according to current diagnostic criteria. All polyps were assessed for BRAF V600E mutation using multiplex kits, tested for KRAS mutation, and had Claudin-1 immunohistochemistry performed. Results Of 377 cases, 174 were re-classified as SSAs, and 203 as MVHP/SP. Claudin-1 positive spindle cells were present in 9.3% (35/377). Twenty-four of 35 polyps with Claudin-1 positive stromal cells were SSAs, 9 were SP and 2 were MVHPs. Twenty-nine of the 35 Claudin-1 positive cases (82%) harboured BRAF V600E mutation. None of the polyps were KRAS positive. Discussion Perineural-like stromal proliferations have been recently described in 6.5% of BRAF V600E positive SSAs and intestinal perineuromas which are characterised by spindle cells obliterating lamina propria and expressing Claudin-1 protein. As SPs with BRAFV600E mutations are known to overexpress Claudin-1, demonstration of Claudin-1 in the stromal cells is a strong indication of epithelial-mesenchymal interactions in BRAF positive serrated polyps. Claudin-1 immunohistochemistry may also aid in diagnosing colorectal polyps containing spindle cells. To analyse the frequency of Claudin-1 positive proliferations in serrated colorectal polyps. Consecutive colorectal polyps originally diagnosed as sessile serrated adenomas (SSAs) and large hyperplastic polyps were reviewed and reclassified as SSAs, microvesicular hyperplastic polyps (MVHP), or serrated polyps (SP) according to current diagnostic criteria. All polyps were assessed for BRAF V600E mutation using multiplex kits, tested for KRAS mutation, and had Claudin-1 immunohistochemistry performed. Of 377 cases, 174 were re-classified as SSAs, and 203 as MVHP/SP. Claudin-1 positive spindle cells were present in 9.3% (35/377). Twenty-four of 35 polyps with Claudin-1 positive stromal cells were SSAs, 9 were SP and 2 were MVHPs. Twenty-nine of the 35 Claudin-1 positive cases (82%) harboured BRAF V600E mutation. None of the polyps were KRAS positive. Perineural-like stromal proliferations have been recently described in 6.5% of BRAF V600E positive SSAs and intestinal perineuromas which are characterised by spindle cells obliterating lamina propria and expressing Claudin-1 protein. As SPs with BRAFV600E mutations are known to overexpress Claudin-1, demonstration of Claudin-1 in the stromal cells is a strong indication of epithelial-mesenchymal interactions in BRAF positive serrated polyps. Claudin-1 immunohistochemistry may also aid in diagnosing colorectal polyps containing spindle cells.

Epidemiology of goblet cell and microvesicular hyperplastic polyps.

Serrated polyps compromise both typical hyperplastic polyps as well as sessile serrated adenomas and dysplastic serrated polyps. Hyperplastic polyps exhibit two histological patterns: microvesicular hyperplastic polyps (MVHPs) and goblet cell hyperplastic polyps (GCHPs). MVHPs and GCHPs differ in their molecular signature. MVHPs have been frequently found to have the BRAF(V600E) mutation as well as aberrant methylation. In contrast, GCHPs have been associated with the KRAS mutation (KRAS-mut), which are infrequently seen in dysplastic serrated sessile adenomas. The particular risk factors that are associated with development of the types of hyperplastic polyps have not been previously studied. The purpose of this study is to characterize the associations between particular risk factors and the development of goblet cell or microvesicular hyperplastic polyps. We conducted a cross-sectional analysis of 3,543 asymptomatic, mostly average risk patients 50 and 79 years of age undergoing open-access screening colonoscopy between March 2005 and January 2012. Each patient was given a survey regarding 25 reputed risk factors for colorectal neoplasia and the responses were correlated with findings at colonoscopy. Associations between putative risk factors for colorectal neoplasia and MVHPs and GSHPs were examined using multiple logistic regression. MVHPS and GCHPs were identified in 5.3% and 8.7% of patients, respectively. The results of the statistical analysis indicate that a history of smoking greater than 20 years is associated with an increased risk of MVHPs (P<0.005) and GCHPs (P<0.005). An elevated BMI >30 kg/m(2) was also associated with the presence of MVHP at colonoscopy (P<0.005). Blacks and Asians appear to be protected from the development of MVHPs. In contrast, there was a positive association with the presence of GCHP at colonoscopy in blacks. The study suggests that the development of the distinct histological types of hyperplastic polyps are associated with distinct modifiable and non-modifiable lifestyle factors.

Molecular features of colorectal polyps presenting Kudo’s type II mucosal crypt pattern: are they based on the same mechanism of tumorigenesis?

Background and study aims: The molecular features of serrated polyps (SPs) with hyperplastic crypt pattern, also called Kudo’s type II observed by chromoendoscopy, were evaluated. Methods: The clinicopathological and molecular features of 114 SPs with a hyperplastic pit pattern detected under chromoendoscopy (five dysplastic SPs, 63 sessile serrated adenoma/polyps (SSA/Ps), 36 microvesicular hyperplastic polyps (MVHPs), and 10 goblet cell-rich hyperplastic polyps (GCHPs)) were examined. The frequency of KRAS and BRAF mutations and CpG island methylator phenotype (CIMP) were investigated. Results: Dysplastic SPs and SSA/Ps were frequently located in the proximal colon compared to others (SSA/Ps vs. MVHPs or GCHPs, P < 0.0001). No significant difference was found in the frequency of BRAF mutation among SPs apart from GCHP (60 % for dysplastic SPs, 44 % for SSA/Ps, 47 % for MVHPs, and 0 % for GCHPs). The frequency of CIMP was higher in dysplastic SPs or SSA/Ps than in MVHPs or GCHPs (60 % for dysplastic SPs, 56 % for SSA/Ps, 32 % for MVHPs, and 10 % for GCHPs) (SSA/Ps vs. GCHP, P = 0.0068). When serrated neoplasias (SNs) and MVHPs were classified into proximal and distal lesions, the frequency of CIMP was significantly higher in the proximal compared to the distal SNs (64 % vs. 11 %, P = 0.0032). Finally, multivariate analysis showed that proximal location and BRAF mutation were significantly associated with an increased risk of CIMP. Conclusions: Distinct molecular features were observed between proximal and distal SPs with hyperplastic crypt pattern. Proximal MVHPs may develop more frequently through SSA/Ps to CIMP cancers than distal MVHPs.

Claudin-1 Expression Is Elevated in Colorectal Cancer Precursor Lesions Harboring the BRAF V600E Mutation

BACKGROUND: Sessile serrated adenomas/polyps (SSA/P) are now recognised precursors of colorectal cancer (CRC) including cancers harbouring somatic BRAF (V600E) mutations. While the morphological diagnostic criteria of SSA/P have been established, distinguishing between small/early SSA/P and microvesicular hyperplastic polyps (MVHP) is challenging and may not be possible in routine practice. METHODS: Gene expression profiling of MVHP (n=5, all BRAF V600E wild-type) and SSA/P (n=5, all BRAF V600E mutant) samples was performed. Quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and immunohistochemical analysis was performed to verify the expression of claudin 1 (CLDN1) in MVHP and SSA/P. RESULTS: Gene expression profiling studies conducted between MVHP and SSA/P identified CLDN1 as the most statistically significant differentially expressed gene (p<0.05). Validation with qRT-PCR confirmed an up-regulation of CLDN1 in BRAF V600E mutant polyps regardless of polyp type (p<0.0005). Immunohistochemical analysis of CLDN1 expression in BRAF V600E mutant SSA/Ps (n=53) and MVHPs (n=111) and BRAF wild-type MVHPs (n=58), demonstrated a strong correlation between CLDN1 expression and the BRAF V600E mutation in both SSA/P and MVHP samples when compared to wild-type polyps (p<0.0001). CONCLUSION: This study demonstrates an up regulation of CLDN1 protein in serrated colorectal polyps including MVHP harbouring the BRAF V600E mutation. Our results demonstrated an apparent heterogeneity on the molecular level within the MVHP group and suggest that MVHP with somatic BRAF V600E mutation and up-regulated expression of CLDN1 are closely related to SSA/P and may in fact represent a continuous spectrum of the same neoplastic process within the serrated pathway of colorectal carcinogenesis.

Intermediate serrated polyp as an intermediate lesion of hyperplastic polyp and sessile serrated polyp/adenoma in terms of morphological and molecular features.

Although a hyperplastic polyp (HP) shares morphological and molecular features with a sessile serrated adenoma/polyp (SSA/P), HPs and SSA/Ps are considered nonneoplastic and neoplastic epithelial polyps, respectively. Because HPs and SSA/Ps cover the morphological spectrum, we hypothesized that an intermediate serrated polyp (ISP) might exist between an HP and an SSA/P in terms of both morphological and molecular aspects. An ISP was defined as a serrated lesion that carries distorted crypts (columnar crypt dilation, irregularly branching crypts, or horizontally arranged basal crypts) in less than 3 consecutive crypts. We analyzed HPs (microvesicular, n = 16, and goblet cell-rich, n = 28), ISPs (n = 44), and SSA/Ps (n = 26) for their methylation status of 8 CpG island methylator phenotype panel markers and mutation status of KRAS/BRAF. The number of methylated markers and BRAF mutation frequency increased in the order of HP, ISP, and SSA/P. Microvesicular HPs and goblet cell-rich HPs are distinct from each other, based on the high frequency of BRAF and KRAS mutation, respectively, but are not different in the number of methylated panel markers. Proximally located microvesicular HPs and ISPs were higher in the number of methylated markers but lower in the frequency of BRAF mutation than distally located ones. However, SSA/Ps did not show any difference in the number of methylated markers and the frequency of BRAF mutation between proximally and distally located lesions. Our findings that serrated polyps, intermediate between HPs and SSA/Ps in terms of morphological features, display molecular alterations intermediate between those of HPs and SSA/Ps suggest the presence of ISPs between HPs and SSA/Ps.

683 Molecular Features of Colorectal Polyps Presenting Kudo's Type II Mucosal Crypt Pattern

Molecular Features of Colorectal Polyps Presenting Kudo’s Type II Mucosal Crypt Pattern Kensuke Shinmura*, Kazuo Konishi, Yutaro Kubota, Yuichiro Yano, Hisako Nozawa, Atsushi Katagiri, Takashi Muramoto, Yoshiya Kobayashi, Toshihiro Kihara, Masayuki Tojo, Kenichi Konda, Teppei Tagawa, Toshiko Yamochi, Fumio Takimoto, Hitoshi Yoshida Division of Gastroenterology, Department of Medicine, Showa University, Tokyo, Japan; Department of Pathology, Showa University, Tokyo, Japan Background & Aims: Hyperplastic polyp (HP), sessile serrated adenoma (SSA) and traditional serrated adenoma (TSA) are thought to be precursor lesions of serrated pathway. However, hyperplastic mucosal crypt patterns (so-called Kudo’s type II) are frequently observed in these lesions under chromoendoscopy. We hypothesized that there are biological or molecular differences among the serrated polyps (SPs) with hyperplastic crypt pattern and that these features are associated with their different pathways of progression to CRC. To test this hypothesis, we evaluated the molecular features of SPs with hyperplastic crypt pattern. Methods: We examined the clinicopathological and molecular features of 136 SPs with hyperplastic [stellar or papillary pits] crypt pattern that were resected endoscopically at Showa University Hospital from April 2005 to November 2011. We investigated the frequency of mutations of KRAS and BRAF; microsatellite instability (MSI); and CpG island methylator phenotype (CIMP), including the methylation of two or more CIMP-related genes (MINT1, 2, 31, p16, and MLH1). HPs were classified into microvesicular HP (MVHP), goblet cell-rich HP (GCHP), and mucin-poor HP (MPHP) variants on the basis of WHO classification. Results: 136 SPs with hyperplastic pattern comprised 81 serrated neoplasias (SNs) (21 TSAs, 60 SSAs), 43 MVHPs and 12 GCHPs. TSAs and SSAs were frequently located in the proximal colon, compared to others (P 0.01). We found no significant difference in the frequency of BRAF mutation among SPs except GCHP (57% for TSAs, 54% for SSAs, 49% for MVHPs and 9% for GCHPs). Furthermore, a significant difference was observed in the frequency of CIMP between TSAs or SSAs and GCHPs (52% for TSAs, 48% for SSAs, 30% for MVHPs and 0% for GCHPs) (P 0.05). When we classified SNs and MVHPs into proximal and distal lesions, proximal lesions had a macroscopically superficial appearance, whereas distal lesions had a protruding appearance (P 0.01). Moreover, the frequency of CIMP was significantly higher in the proximal than the distal lesions (55% vs. 16%) (P 0.05). Conclusions: We observed distinct molecular features between proximal and distal SPs with hyperplastic crypt pattern. Proximal SPs with hyperplastic pattern may develop from MVHPs through SSAs/TSAs to colon cancers.