Molecular alterations in chronic ulcerative colitis-associated and sporadic hyperplastic polyps: a comparative analysis

Pathology and Clinical Significance of Inflammatory Bowel Disease-Associated Colorectal Dysplastic Lesions

Timely diagnosis and effective management of colorectal dysplasia play a vital role in preventing mortality from colorectal cancer in patients with chronic inflammatory bowel disease. This review provides a contemporary overview of the pathologic and endoscopic classification of dysplasia in inflammatory bowel disease, their roles in determining surveillance and management algorithms, and emerging diagnostic and therapeutic approaches that might further enhance patient management.

Colorectal dysplasia in chronic inflammatory bowel disease: a contemporary consensus classification and interobserver study

The clinical management of patients with dysplasia in chronic inflammatory bowel disease (IBD) is currently guided by Riddell et al.'s grading system (negative, indefinite, low grade, high grade) from 1983 which was based primarily on nuclear cytoarchitectural characteristics. Although most dysplasia in IBD resembles sporadic adenomas morphologically, other distinctive potential cancer precursors in IBD have been described over time. Recognizing the need for a updated comprehensive classification for IBD-associated dysplasia, an international working group of pathologists with extensive clinical and research experience in IBD devised a new classification system and assessed its reproducibility by having each participant assess test cases selected randomly from a repository of electronic images of potential cancer precursor lesions. The new classification system now encompasses three broad categories and nine sub-categories: 1) intestinal dysplasia (tubular/villous adenoma-like, goblet cell deficient, crypt cell, traditional serrated adenoma-like, sessile serrated lesion-like and serrated NOS), 2) gastric dysplasia (tubular/villous and serrated), and 3) mixed intestinal-gastric dysplasia. In the interobserver analysis, 67% of the diagnoses were considered definitive and achieved substantial inter-rater agreement. The key distinctions between intestinal and gastric lesions and between serrated and non-serrated lesions achieved substantial and moderate inter-rater agreement overall, respectively, however, the distinctions among certain serrated sub-categories achieved only fair agreement. Based on the Riddell grading system, definite dysplasia accounted for 86% of the collective responses (75% low grade, 11% high grade). Based on these results, this new classification of dysplasia in IBD can provide a sound foundation for future clinical and basic IBD research.

Influence of SCENIC recommendations on terminology used for histopathologic diagnosis of inflammatory bowel disease-associated dysplasia

BACKGROUND

Published in 2015, the International Consensus Recommendations on Surveillance for Colorectal Endoscopic Neoplasia Detection and Management in Inflammatory Bowel Disease Patients (SCENIC) recommended abandoning the use of diagnostic term “dysplasia-associated lesion or mass (DALM)” for polypoid dysplastic lesions detected in patients with inflammatory bowel disease (IBD). The aim of this study was to investigate whether this recommendation had any influence on diagnostic terminologies used by pathologists in their practice.

METHODS

We retrospectively reviewed all pathology reports for surveillance colonoscopic biopsies from ulcerative colitis (UC) patients in our institution during 1/2012-12/2014 (pre-SCENIC) and 1/2016-12/2018 (post-SCENIC). These included 1203 biopsies from 901 UC patients during the pre-SCENIC period and 1273 biopsies from 977 UC patients during the post-SCENIC period. Their corresponding endoscopic findings and histopathologic diagnoses were recorded. Clinical indications for total colectomy for UC patients and corresponding histopathologic findings in colectomy specimens were also recorded and compared.

RESULTS

A total of 347 and 419 polyps/polypoid lesions were identified during the pre-SCENIC and post-SCENIC periods, among which 60 and 104 were dysplastic/ adenomatous, respectively. More polypoid dysplastic lesions were simply diagnosed as “adenoma” during the post-SCENIC period in comparison with the pre-SCENIC period (97.1% vs 65.0%; P < 0.001). The number of cases with a comment in pathology reports regarding the distinction between DALM and sporadic adenoma was also significantly decreased during the post-SCENIC period (5.8% vs 38.3%; P < 0.001). In addition, the term “dysplasia” was more consistently used for random biopsies during the post-SCENIC period. Furthermore, the terms “sessile serrated adenoma/polyp” (SSA/P) and “serrated epithelial change” (SEC) were more consistently used for polypoid lesions and random biopsies, respectively, during the post-SCENIC period, although these were not specifically addressed in the SCENIC recommendations. The indications for colectomy remained unchanged, however, despite the standardization of diagnostic terminologies.

CONCLUSION

The SCENIC recommendations relieve pathologists from the burden of distinguishing DALM from sporadic adenoma in IBD patients, which helps the standardization of diagnostic terminologies used by pathologists. The consistent use of the diagnostic terminologies may help reduce potential confusions to clinicians and patients.

Increased Colorectal Neoplasia Risk in Patients with Inflammatory Bowel Disease and Serrated Polyps with Dysplasia

BACKGROUND

The impact of serrated polyps on the advanced colorectal neoplasia (CRN) risk in inflammatory bowel disease (IBD) patients is unknown. Serrated polyps are histologically categorized as hyperplastic polyps (HPs), sessile serrated lesions (SSLs), and traditional serrated adenomas (TSAs).

AIMS

We aimed (1) to characterize the serrated polyps in IBD patients, (2) to identify factors associated with the presence of serrated polyps in IBD, and (3) to assess the CRN risk in IBD patients with serrated polyps.

METHODS

We established a retrospective cohort of IBD patients with and without colonic serrated polyps. Cox-regression analysis with time-dependent variables was used to compare advanced CRN risk in IBD patients with and without serrated polyps.

RESULTS

Of the 621 enrolled IBD patients, 198 had a serrated polyp (92 HPs, 88 SSLs without dysplasia, 13 SSLs with dysplasia, and 5 TSAs). Independent factors associated with serrated polyps were ulcerative colitis (UC) (odds ratio (OR) 1.77, 95% confidence interval (CI) 1.19-2.62, p = 0.005), male gender (OR 1.63, 95% CI 1.11-2.40, p = 0.013), and older age (per year increase, OR 1.06, 95%CI 1.05-1.08, p < 0.001). TSAs and SSLs with dysplasia were risk factors for subsequent advanced CRN (HR 13.51, 95% CI 3.11-58.68, p < 0.001), while HPs (HR 1.98, 95% CI 0.46-8.60, p = 0.36) and SSLs without dysplasia (HR 0.87, 95% CI 0.11-6.88, p-0.89) did not impact the subsequent advanced CRN risk.

CONCLUSIONS

UC, male gender and older age were associated with the presence of serrated polyps. The majority of serrated polyps (91%) were HPs and SSL without dysplasia and did not affect the CRC risk. However TSAs and SSLs with dysplasia, representing a small subgroup of serrated polyps (9%), were associated with subsequent advanced CRN.

Non-conventional dysplasia in inflammatory bowel disease is more frequently associated with advanced neoplasia and aneuploidy than conventional dysplasia

AIMS

Several different non-conventional morphological patterns of epithelial dysplasia have been recently described in inflammatory bowel disease (IBD), but there is limited information regarding their clinicopathological and molecular features, as well as potential risk for high-grade dysplasia (HGD) or colorectal cancer (CRC) compared with conventional dysplasia developing in IBD.

METHODS AND RESULTS

A total of 317 dysplastic lesions from 168 IBD patients were analysed. All lesions were re-reviewed and subtyped as either conventional [including tubular adenoma-like (n = 183) and tubulovillous/villous adenoma-like (n = 56)] or non-conventional dysplasia [including dysplasia with increased Paneth cell differentiation (DPD, n = 40), crypt cell dysplasia (CCD, n = 14), goblet cell deficient (GCD, n = 10), hypermucinous (n = 7), sessile serrated lesion (SSL)-like (n = 4) and traditional serrated adenoma (TSA)-like (n = 3)]. DNA flow cytometry was performed on 70 low-grade conventional (n = 24) and non-conventional (n = 46) dysplastic biopsies to determine their malignant potential and molecular pathways to HGD or CRC. Eleven sporadic tubular adenomas with low-grade dysplasia (LGD) were utilised as controls. Seventy-eight non-conventional dysplastic lesions were identified in 56 (33%) of the 168 patients, whereas 239 conventional dysplastic lesions were identified in 149 (89%) patients. Although both non-conventional and conventional dysplasias were most often graded as LGD at diagnosis (83% and 84%, respectively), non-conventional dysplasia (38%) was more likely to develop HGD or CRC in the same colonic segment than conventional dysplasia (19%) on follow-up (P < 0.001). Almost half (46%) of non-conventional dysplastic samples showed aneuploidy, whereas only 8% of conventional dysplasia (P = 0.002) and 9% of sporadic tubular adenomas (P = 0.037) did. Also, non-conventional dysplasia more frequently presented as a flat/invisible lesion (41%) compared with conventional dysplasia (18%) (P < 0.001). Among the non-conventional subtypes (n = 78), DPD was the most common (n = 40; 51%), followed by CCD (n = 14; 18%), GCD (n = 10; 13%), hypermucinous (n = 7; 9%), SSL-like (n = 4; 5%) and TSA-like (n = 3; 4%) variants. Hypermucinous dysplasia (mean = 2.1 cm) was significantly larger than DPD, SSL-like, TSA-like and GCD variants (mean = 1.0, 1.2, 1.2 and 1.9 cm, respectively) (P = 0.037). HGD or CRC was more likely to be associated with CCD (n = 13; 93%), hypermucinous (n = 4; 57%), GCD (n = 4; 40%) and SSL-like (n = 3; 75%) variants than DPD (n = 6; 15%) and TSA-like dysplasia (n = 0; 0%) on follow-up (P < 0.001). Furthermore, the rate of aneuploidy was significantly higher in CCD (100%), hypermucinous (80%) and GCD (25%) variants than in DPD (12%), SSL-like dysplasia (0%) and TSA-like dysplasia (0%) (P < 0.001).

CONCLUSIONS

Non-conventional morphological patterns of dysplasia are not uncommon in IBD, detected in 33% of the patients. The higher frequencies of advanced neoplasia (HGD or CRC) and aneuploidy in non-conventional dysplasia, in particular CCD, hypermucinous and GCD variants, suggest that they may have a higher malignant potential than conventional dysplasia or sporadic tubular adenomas, and thus need complete removal and/or careful follow-up. Greater than 40% of non-conventional dysplasia presented as a flat/invisible lesion, suggesting that IBD patients may benefit from random biopsy sampling in addition to targeted biopsies. The majority of non-conventional subtypes appear to develop via the chromosomal instability pathway, whereas an alternative serrated pathway may be responsible for the development of at least a subset of SSL-like and TSA-like dysplasias.

Significance of serrated epithelial change in inflammatory bowel disease

OBJECTIVES

The clinical significance of hyperplastic polyp-like histologic changes in random biopsy samples ('serrated epithelial change' or SEC) from patients with inflammatory bowel disease (IBD) remains uncertain, with some studies suggesting an increased risk of dysplasia and even carcinoma. Controlled studies are few. We studied the significance of SEC on the development of dysplasia in follow-up surveillance of IBD patients in our system.

METHODS

We identified 94 IBD patients with SEC and 187 IBD patients without SEC identified in index biopsy samples, and retrospectively collated results of follow-up surveillance samples in each group, with the development of dysplasia and/or adenocarcinoma as study endpoints.

RESULTS

IBD patients with SEC had a 12.8% likelihood of developing dysplasia of any type within IBD-affected areas vs a 4.3% likelihood in non-SEC patients (follow-up in the 1-4 year range for each group). This was significant in univariate analysis (p = 0.013) but not in multivariate analysis, likely due to increased frequency of follow-up sampling in the SEC patients. One cancer developed in each group (p = NS).

CONCLUSION

Our data, in the context of other studies, neither prove nor conclusively exclude an increased risk of dysplasia in IBD patients with SEC. But cancer risk appears low and continued surveillance at usual intervals seems reasonable.

Nonconventional dysplasia in patients with inflammatory bowel disease and colorectal carcinoma: a multicenter clinicopathologic study

Several types of nonconventional dysplasia have been recently described in inflammatory bowel disease (IBD). However, strict morphologic criteria are lacking, and their clinicopathologic features (including potential association with conventional dysplasia and/or colorectal cancer [CRC]) are poorly understood. A total of 106 dysplastic or serrated lesions in 58 IBD patients with CRC were retrospectively identified from five institutions. Thirty-six cases of nonconventional dysplasia were identified in 26 (45%) of the 58 patients and occurred with similar frequency in men and women (58% and 42%, respectively), with a mean age of 54 years (range: 24-73) and a long history of IBD (mean: 17 years, range: 2-43). Six morphologic patterns were recognized. Hypermucinous dysplasia (n = 15; 42%) presented as either a 'pure type' (n = 5; 14%) or a 'mixed type' with either conventional or another nonconventional subtype (n = 10; 28%). Serrated lesions, as a group, were equally common (n = 15; 42%) and included three variants: traditional serrated adenoma-like (n = 10; 28%), sessile serrated lesion-like (n = 1; 3%), and serrated lesion, not otherwise specified (n = 4; 11%). Dysplastic lesions with increased Paneth cell differentiation (n = 4; 11%) and goblet cell deficient dysplasia (n = 2; 6%) were rare. Twelve (46%) of the 26 patients had only nonconventional dysplasia, whereas the remaining 14 patients (54%) had both nonconventional and conventional dysplasias. Nonconventional dysplasia was most often graded as low-grade dysplasia (81%), which was less common in conventional dysplasia (37%) (p = 0.003). When present alone, nonconventional dysplasia was predominantly found in the left colon (81%, p = 0.006) as a polypoid or raised lesion (75%, p < 0.001) compared with when it occurred simultaneously with conventional dysplasia (35% and 50%, respectively). When both nonconventional and conventional dysplasias occurred simultaneously, they were found in the same colonic segment in all but 3 patients (79%). Nonconventional dysplasia was also commonly detected in the same colonic segment as CRC or immediately adjacent to the CRC at a rate (85%) similar to conventional dysplasia (96%). CRC occurring in patients with only nonconventional dysplasia was more likely to be high-grade (poorly differentiated; 36%) than CRC that occurred in association with conventional dysplasia (10%) (p = 0.026). In conclusion, nonconventional dysplasia is common in IBD patients with CRC. It appears to develop in the same field of carcinomatous development, and it is not uncommonly associated with conventional dysplasia.

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.

Chromoendoscopy versus autofluorescence imaging for neoplasia detection in patients with longstanding ulcerative colitis (FIND-UC): an international, multicentre, randomised controlled trial

BACKGROUND

Patients with longstanding ulcerative colitis undergo regular dysplasia surveillance because they have an increased colorectal cancer risk. Autofluorescence imaging and chromoendoscopy improve dysplasia detection. The aim of this study was to determine whether autofluorescence imaging should be further studied as an alternative method for dysplasia surveillance in patients with longstanding ulcerative colitis.

METHODS

This prospective, international, randomised controlled trial included patients from an ulcerative colitis-dysplasia surveillance cohort from five centres in the Netherlands and the UK. Eligible patients were aged 18 years or older who were undergoing dysplasia surveillance after being diagnosed with extensive colitis (Montreal E3) at least 8 years before study start or with left-sided colitis (Montreal E2) at least 15 years before study start. Randomisation (1:1) was minimised for a previous personal history of histologically proven dysplasia and concomitant primary sclerosing cholangitis. The coprimary outcomes were the proportion of patients in whom at least one dysplastic lesion was detected and the mean number of dysplastic lesions per patient. The relative dysplasia detection rate, calculated as the ratio of the detection rates by autofluorescence imaging and chromoendoscopy, needed to be more than 0·67 (using an 80% CI) for both primary outcomes to support a subsequent large non-inferiority trial. Outcomes were analysed on a per-protocol basis. The trial is registered at the Netherlands Trial Register, number NTR4062.

FINDINGS

Between Aug 1, 2013, and March 10, 2017, 210 patients undergoing colonoscopy surveillance for longstanding ulcerative colitis were randomised for inspection with either autofluorescence imaging (n=105) or chromoendoscopy (n=105). Dysplasia was detected in 13 (12%) patients by autofluorescence imaging and in 20 patients (19%) by chromoendoscopy. The relative dysplasia detection rate of autofluorescence imaging versus chromoendoscopy for the proportion of patients with ulcerative colitis with at least one dysplastic lesion was 0·65 (80% CI 0·43-0·99). The mean number of detected dysplastic lesions per patient was 0·13 (SD 0·37) for autofluorescence imaging and 0·37 (1·02) for chromoendoscopy (relative dysplasia detection rate 0·36, 80% CI 0·21-0·61). Adverse events were reported for two patients in the autofluorescence imaging group (one patient had intraprocedural mild bleeding, and one patient had abdominal pain) and for three patients in the chromoendoscopy group (two patients had intraprocedural mild bleeding, and one patient had perforation).

INTERPRETATION

Autofluorescence imaging did not meet criteria for proceeding to a large non-inferiority trial. Therefore, existing autofluorescence imaging technology should not be further investigated as an alternative dysplasia surveillance method.

FUNDING

Olympus Europe and Olympus Keymed.

British Society of Gastroenterology position statement on serrated polyps in the colon and rectum

Serrated polyps have been recognised in the last decade as important premalignant lesions accounting for between 15% and 30% of colorectal cancers. There is therefore a clinical need for guidance on how to manage these lesions; however, the evidence base is limited. A working group was commission by the British Society of Gastroenterology (BSG) Endoscopy section to review the available evidence and develop a position statement to provide clinical guidance until the evidence becomes available to support a formal guideline. The scope of the position statement was wide-ranging and included: evidence that serrated lesions have premalignant potential; detection and resection of serrated lesions; surveillance strategies after detection of serrated lesions; special situations-serrated polyposis syndrome (including surgery) and serrated lesions in colitis; education, audit and benchmarks and research questions. Statements on these issues were proposed where the evidence was deemed sufficient, and re-evaluated modified via a Delphi process until >80% agreement was reached. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) tool was used to assess the strength of evidence and strength of recommendation for finalised statements. Key recommendation: we suggest that until further evidence on the efficacy or otherwise of surveillance are published, patients with sessile serrated lesions (SSLs) that appear associated with a higher risk of future neoplasia or colorectal cancer (SSLs ≥10 mm or serrated lesions harbouring dysplasia including traditional serrated adenomas) should be offered a one-off colonoscopic surveillance examination at 3 years (weak recommendation, low quality evidence, 90% agreement).

The Significance of Sessile Serrated Polyps in Inflammatory Bowel Disease

BACKGROUND

The significance of serrated lesions in inflammatory bowel disease (IBD) remains unclear. We aim to characterize synchronous and metachronous lesions in IBD patients with an index serrated polyp and compare them to sporadic subjects with SSP.

METHODS

Serrated lesions in patients with IBD were identified from a pathology database and, after review, were reclassified as hyperplastic (HP), sessile serrated (SSPs), or serrated polyps unclassifiable (SPU).

RESULTS

One hundred thirty-four IBD patients were found to have 147 serrated polyps at index colonoscopy. SSPs were more likely to be located in the right colon: SSP (76.0%), SPU (41.7%) and HP (27.8%); P = 0.002. Synchronous multifocal visible dysplasia occurred more frequently in the SSP or SPU groups (44.5% and 66%) compared to the HP group (12%); P = 0.031. Among 13 IBD patients with index SSP followed over a median of 6 years, 61.5% developed metachronous visible dysplasia or additional SSPs. Larger index SSP size was associated with higher risk of developing subsequent visible dysplasia with a 10% increase for every 1 mm increase in size (HR = 1.1; P = 0.028), but was not associated with developing subsequent SSP (P = 0.50). The risk of subsequent SSP or visible dysplasia was no different between the IBD and non-IBD groups, but there was a trend suggesting SSP may be a marker of increased early risk of metachronous visible dysplasia in IBD patients.

CONCLUSIONS

IBD patients with an index SSP and SPU have a heightened risk of synchronous multifocal visible dysplasia. Additionally, IBD patients with SSP may be at risk of early metachronous visible dysplasia.

Molecular Alterations of Colorectal Cancer with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an important etiologic factor in the development of colorectal cancer (CRC). The risk of CRC begins to increase 8 or 10 years after the diagnosis of IBD. This type of cancer is called colitis-associated CRC (CA-CRC). The molecular pathogenesis of inflammatory epithelium might play a critical role in the development of CA-CRC. Genetic alterations detected in CA-CRC such as genetic mutations, microsatellite instability, and DNA hypermethylation are also recognized in sporadic CRC; however, there are differences in the timing and frequency of molecular events between CA-CRC and sporadic CRC. Interaction between gene-environmental factors, including inflammation, lifestyle, psychological stress, and prior appendectomy, might be associated with the etiopathology of IBD. The mucosal inflammatory mediators, such as oxidant stress, free radicals, and chemokines, may cause the genetic alterations. Understanding the molecular mechanisms of CA-CRC might be important to develop clinical efficacies for patients with IBD. This review discusses the molecular characteristics of CA-CRC, especially ulcerative colitis-associated CRC, including clinical features, signaling pathways, and interactions between genetic alterations and environment involved in inflammatory carcinogenesis.

Hyperplastic polyp of the duodenum: a report of 9 cases with immunohistochemical and molecular findings

Benign serrated polyps are commonly found in the colorectum but have rarely been described in other parts of the gastrointestinal tract. We report a series of 9 serrated polyps arising in the duodenum with clinicopathologic features, immunohistochemical expression profile of mucins (MUC2, MUC5AC, MUC6), and molecular analysis for BRAF and KRAS. The polyps were diagnosed as incidental endoscopy findings in 9 different patients, comprising 3 male and 6 female patients, with a mean age of 52.2 years (range, 21-72 years). The second part of the duodenum was the most common site (n = 5), followed by the ampulla (n = 1) and the distal duodenum (n = 1), with the location of the 2 remaining polyps unspecified. Other upper gastrointestinal tract pathology features included Barrett esophagus for 5 patients, Helicobacter gastritis for 1 patient, and mild chronic gastritis for 1 patient. The histologic appearance of the polyps was similar to microvesicular hyperplastic polyp in the colorectum. Immunostaining for mucins showed MUC6 expression in the crypt bases of all polyps, MUC5AC expression in 8 cases (89%), and mucin 2 expression in 6 cases (67%). Molecular testing was successful in 6 polyps, showing BRAF mutation (V600E) in 2 polyps, KRAS mutation in 2 polyps, and no mutation for either gene in 2 polyps. Colonoscopy reports were available for 6 patients, of whom 4 were diagnosed with hyperplastic polyps or sessile serrated polyps in the colorectum. However, no patient met the criteria for serrated polyposis. Although probably rare and of uncertain malignant potential, hyperplastic polyp should be considered in the differential diagnosis of benign duodenal polyp.

Pathologic features and biologic importance of colorectal serrated polyps

Serrated polyps of the large intestine comprise a heterogeneous group of mucosal lesions that includes nondysplastic polyps, such as hyperplastic polyps and sessile serrated polyps, and polyps that show overt cytologic dysplasia, namely serrated adenomas and mixed hyperplastic/adenomatous polyps. These polyps have received increased recognition over the past 2 decades, as emerging evidence suggests that a subset may be precursors to colorectal carcinomas that lack chromosomal instability. Several investigators have proposed the concept of the "serrated neoplastic pathway" according to which nondysplastic serrated lesions develop progressively severe dysplasia culminating in the development of microsatellite unstable carcinomas that show DNA hypermethylation and BRAF mutations. A subset of hyperplastic polyps and sessile serrated polyps show mutations in the BRAF gene and abnormal DNA methylation, which can, ultimately, affect the promoter regions of key DNA-repair and tumor suppressor genes, such as MLH1 and MGMT, leading to their decreased transcription and microsatellite instability. On the basis of this hypothesis, many authors have proposed that sessile serrated polyps should be treated and surveilled similar to conventional adenomas, although prospective data are lacking. This review describes the clinicopathologic and molecular features of serrated polyps and discusses the current data regarding their biologic significance.

Hyperplastic/serrated polyposis in inflammatory bowel disease: a case series of a previously undescribed entity

Herein, we describe the clinical, pathologic, immunohistochemical, and molecular features of 3 unique patients with long standing inflammatory bowel disease, all of whom developed numerous discrete hyperplastic/serrated colonic polyps similar to those described in the hyperplastic/serrated polyposis syndrome. The 3 patients (2 with ulcerative colitis and 1 with Crohn ileo-colitis) were evaluated for a variety of clinical, histologic (including the type, location and number of polyps in the colon), and immunohistochemical features [MLH-1, MSH-2, MGMT (O(6)-methylguanine-DNA methyltransferase), beta-catenin, and p53]. KRAS and BRAF mutation analysis was also performed on a subset of polyps from 2 patients. All patients had moderate-severe pancolitis of more than 10 years duration and had >20 colonic polyps. None had polyps in the upper gastrointestinal tract. Pathologically, a combination of conventional hyperplastic polyps and sessile serrated polyps (adenomas) were present in the 3 cases. In addition, serrated adenomas were present in 2 and conventional adenomas in 1. Two patients also had synchronous adenocarcinoma. All 3 cases showed retention of MLH-1 and MSH-2, and a membranous beta-catenin staining pattern. However, 2 cases showed loss of MGMT in several serrated polyps, and one also in adjacent colitic mucosa. KRAS mutations were detected in 5/11 serrated polyps. However, BRAF mutations were not present in any of the polyps tested. These findings suggest the possibility of a serrated pathway of carcinogenesis in inflammatory bowel disease characterized by silencing of MGMT, most likely by gene promoter methylation, KRAS mutations, and possibly other, as yet, uncharacterized molecular alterations, resulting eventually in progression to adenocarcinoma.

Pathology of early lower GI cancer

Early colorectal cancer can be treated with curative resection if the depth of invasion is limited to the submucosa (pathologic T category pT1 in the TNM classification). Macroscopically early colorectal cancer and its precursor lesions present as elevated polyps or non-polypoid flat lesions. Microscopically, precursor lesions are characterized by intraepithelial neoplasia and present as classic adenomas or serrated adenomas. Precursor lesions may already contain foci of early colorectal cancer. Early colorectal cancer can be treated by endoscopic resection. Careful handling of the specimen is required in order to optimally identify the factors that may predict an adverse outcome. Whenever a favourable tumour grade is found, without vascular invasion and tumour budding, there seems to be a low risk for adverse outcome and laparotomy may thus be avoided.

K-ras as a target for cancer therapy

The central role K-, H- and N-Ras play in regulating diverse cellular pathways important for cell growth, differentiation and survival is well established. Dysregulation of Ras proteins by activating mutations, overexpression or upstream activation is common in human tumors. Of the Ras proteins, K-ras is the most frequently mutated and is therefore an attractive target for cancer therapy. The complexity of K-ras signaling presents many opportunities for therapeutic targeting. A number of different approaches aimed at abrogating K-ras activity have been explored in clinical trials. Several of the therapeutic agents tested have demonstrated clinical activity, supporting ongoing development of K-ras targeted therapies. However, many of the agents currently being evaluated have multiple targets and their antitumor effects may not be due to K-Ras inhibition. To date, no selective, specific inhibitor of K-ras is available for routine clinical use. In this review, we will summarize the structure and function of K-ras with attention to its role in tumorigenesis and discuss the successes and failures of the various strategies designed to therapeutically target this important oncogene.

Molecular phenotype of inflammatory bowel disease-associated neoplasms with microsatellite instability

BACKGROUND & AIMS

Patients with inflammatory bowel disease (IBD) are at increased risk of developing colorectal cancer (CRC). We sought to determine the frequency of high-level microsatellite instability (MSI-H) and the mutational and methylation profile of MSI-H IBD-related neoplasms (IBDNs).

METHODS

A total of 124 IBDNs (81 cancers, 43 dysplasias) from 78 patients were studied for the frequency of MSI-H and hypermethylation of 3 target genes: MLH1 , HPP1 , and RAB-32 . Fifteen MSI-H IBDNs were characterized according to their profile of frameshift mutations in 28 mononucleotide repeats and compared with 46 sporadic MSI-H CRCs.

RESULTS

Nineteen of 124 IBDNs were MSI-H. The frequency of frameshift mutations in coding mononucleotide repeats was significantly lower in MSI-H IBDNs than in sporadic MSI-H CRCs for TGFBR2 (7 of 14 vs 34 of 43 samples; P = .047) and ACVR2 (3 of 14 vs 25 of 43 samples; P = .029). In contrast, ICA1 was mutated in 3 of 9 MSI-H IBDNs vs 2 of 54 sporadic MSI-H CRCs ( P = .028). HPP1 and RAB32 methylation was independent of MSI status and was observed in 4 of 59 and 0 of 64 nondysplastic mucosae, 20 of 38 and 1 of 25 dysplasias, and 28 of 61 and 20 of 60 carcinomas, respectively.

CONCLUSIONS

The profiles of coding microsatellite mutations (instabilotypes) differ significantly between MSI-H IBDNs and MSI-H sporadic CRCs. Specifically, TGFBR2 and ACVR2 mutations are significantly rarer in MSI-H IBDNs than in MSI-H sporadic CRCs. Furthermore, HPP1 methylation occurs early, in 7% of nondysplastic and approximately half of dysplastic mucosae, whereas RAB32 methylation occurs at the transition to invasive growth, being rarer in dysplasias.

Support for hMLH1 and MGMT silencing as a mechanism of tumorigenesis in the hyperplastic–adenoma-carcinoma (serrated) carcinogenic pathway in the colon

BACKGROUND

Down-regulation of DNA repair genes has been proposed as an important mechanism of tumorigenesis in some colon cancers. This mechanism has also recently been implicated in the newly postulated hyperplastic polyp-serrated adenoma-carcinoma ("serrated") pathway of carcinogenesis, although this has never been investigated thoroughly. The aim of this study was to evaluate hMLH1, hMSH2, MGMT, as well as MIB-1, p53, and beta-catenin immunoexpression in an uncommon cohort of mixed colonic polyps that contain a combination of hyperplastic and adenomatous features (n = 21), and in some (n = 7), carcinoma as well.

DESIGN

The clinical, pathological, and immunophenotypic (hMLH1, hMSH2, MGMT, MIB-1, p53, and beta-catenin) properties of 28 mixed hyperplastic and adenomatous polyps of the colon (7 of which also contained carcinoma within the same lesion) were evaluated for the above immunopeptides in each of the different morphologic areas of the polyps, and the results were compared to traditional hyperplastic polyps, serrated adenomas, and conventional (nonserrated) adenomas.

RESULTS

Clinically, most mixed polyps with carcinoma occurred in the ascending colon (86%), and pathologically, the adenomatous component of most mixed polyps was serrated (96%). Mixed polyps, particularly those with carcinoma, showed loss of hMLH1 (33%), MGMT (37%), and even hMSH2 (11%) with significantly higher frequency compared to hyperplastic polyps, conventional adenomas, and serrated adenomas. More specifically, loss of hMLH1 and MGMT were more frequent in epithelium of higher neoplastic grade in mixed polyps. However, hMSH2 loss was only present in the adenoma component and never in the hyperplastic or carcinomatous areas of these polyps. Defects in MIB-1 proliferation indices and p53 were not significantly different among the same epithelial components in each of the polyp groups. However, conventional adenomas showed significantly higher rates of nuclear beta -catenin staining (100%) in comparison to the adenomatous component of mixed polyps (60%).

CONCLUSIONS

Loss of hMLH1 and MGMT play a prominent role in the serrated pathway of carcinogenesis in the colon.

Comparative molecular pathology of sporadic hyperplastic polyps and neoplastic lesions from the same individual

AIM

The biology of colorectal hyperplastic polyps is of considerable relevance, because recent evidence suggests that under certain circumstances hyperplastic polyps may be precursors of neoplasms. The aim of this study was to assess and compare the clinical and molecular characteristics of hyperplastic polyps and neoplastic lesions removed from patients without the hyperplastic polyposis syndrome.

METHODS

One hundred and twenty six patients were identified through a series of genetic epidemiological studies. Each patient had at least one neoplastic lesion and one hyperplastic polyp; there was a total of 147 hyperplastic polyps. All lesions were evaluated for K-ras mutations, loss of heterozygosity (LOH) of the adenomatous polyposis coli (APC) gene, and microsatellite instability.

RESULTS

K-ras mutation was detected in 15 (10%) hyperplastic polyps, all from the rectosigmoid colon. No hyperplastic polyp had APC LOH or microsatellite instability. Patients with adenomas or carcinomas showing K-ras mutations were not more likely to have hyperplastic polyps with K-ras mutations. The average number of adenomas did not differ between those patients with hyperplastic polyps with K-ras mutations and those without K-ras mutations. There was no association between the hyperplastic polyp and the adenoma regarding the colon segments from which the two lesions were removed.

CONCLUSIONS

The sporadic hyperplastic polyp is a lesion with limited molecular change and no relation to patients' neoplastic lesions.

Adenomatous colonic polyps are rare in ulcerative colitis

BACKGROUND

Uncertainty exists as to whether dysplastic polyps in ulcerative colitis should always be managed as dysplasia-associated lesions/masses requiring colectomy, or whether some can be managed by polypectomy. The prevalence of non-inflammatory polyps in ulcerative colitis is unknown.

AIM

To compare dysplastic polyp occurrence in patients with ulcerative colitis and in patients without inflammatory bowel disease.

METHODS

The clinical, endoscopic and histological records of 150 ulcerative colitis patients (median disease duration, 10 years; 57% with pancolitis) undergoing colonoscopy were scrutinized for any polyp history. Two hundred and five patients undergoing colonoscopy for altered bowel habit, but without features suggestive of polyp presence, were used as a control group. Immunohistochemical staining of flat and polypoid mucosa for p16, beta-catenin, p53 and cyclo-oxygenase-2 was compared in the two groups.

RESULTS

Only six (4%) ulcerative colitis patients had ever had dysplastic polyps. Two had single adenomatous polyps proximal to the colitis segment. Of the four patients with dysplastic polyps within colitic mucosa, two were treated endoscopically, but in two the lesions were considered to be dysplasia-associated lesions/masses and colectomy was advised. In contrast, 24 controls had at least one adenomatous polyp (chi(2) = 6.7, P < 0.01). Ten (6.7%) ulcerative colitis patients and 24 (12%) control patients had metaplastic polyps (N.S.). Immunohistochemical staining was not discriminatory.

CONCLUSION

Despite the increased cancer risk in long-standing ulcerative colitis, adenomatous polyps arise less frequently in ulcerative colitis patients than in patients without ulcerative colitis.

Bacteria-induced intestinal cancer in mice with disrupted Gpx1 and Gpx2 genes

Two glutathione peroxidase (GPX) isozymes, GPX-1 and GPX-2 (GPX-GI), are the major enzymes that reduce hydroperoxides in intestinal epithelium. We have previously demonstrated that targeted disruption of both the Gpx1 and Gpx2 genes (GPX-DKO) results in a high incidence of ileocolitis in mice raised under conventional conditions, which include the harboring of Helicobacter species [non-specific-pathogen-free (non-SPF) conditions]. In this study, we have characterized GPX-DKO mice that have microflora-associated intestinal cancers, which are correlated with increased intestinal pathology/inflammation. We found that GPX-DKO mice raised under germ-free conditions have virtually no pathology or tumors. After colonizing germ-free mice with commensal microflora without any known pathogens (SPF), <9% of GPX-DKO mice develop tumors in the ileum or the colon. However, about one-fourth of GPX-DKO mice raised under non-SPF conditions from birth or transferred from SPF conditions at weaning have predominantly ileal tumors. Nearly 30% of tumors are cancerous; most are invasive adenocarcinomas and a few signet-ring cell carcinomas. On the basis of these results, we conclude that GPX-DKO mice are highly susceptible to bacteria-associated inflammation and cancer. The sensitivity exhibited in these mice suggests that peroxidative stress plays an important role in ileal and colonic pathology and inflammation, which can lead to tumorigenesis.