Serrated mucosal lesions of the colorectum

Endoscopic analysis of colorectal serrated lesions with cancer

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

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

BACKGROUND/AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Female-specific rectal carcinogenesis in cyclin D1b transgenic mice

Human cyclin D1 generates two major isoforms via alternative splicing: cyclin D1a and cyclin D1b. Cyclin D1b is hardly expressed in normal tissues but is frequently expressed in certain types of cancer tissues. To clarify the oncogenic potential of cyclin D1b variant, we developed cyclin D1b transgenic (Tg) mice and analyzed their phenotypes. We detected rectal tumors in 63% (15/24) of the female Tg mice. All rectal tumors had the histological characteristics similar to human sessile serrated adenoma/polyps (SSA/Ps). Adenocarcinomas were also found in 53% (8/15) of the rectal tumors, suggesting that these adenocarcinomas originated from the SSA/P-like lesions. No rectal tumors were found in the ovariectomized female cyclin D1b Tg mice (0/10), indicating that ovarian hormones played a critical role in rectal carcinogenesis in these Tg mice. Both phosphorylation of Erk, without activating MEK, and expression of estrogen receptor β were elevated in the rectal tumors of female cyclin D1b Tg mice compared with normal rectums of female wild-type mice. In addition, we established a cell line, D1bTgRT, derived from a rectal cancer of female Tg mouse. Small interfering RNA-induced cyclin D1b knockdown in this cell line suppressed Erk phosphorylation, anchorage-independent growth, cell invasiveness and tumorigenicity in nude mice. In humans, expression of cyclin D1b messenger RNA was detected in 17% (1/6) of colorectal cancer cell lines and 9.7% (3/31) of colorectal cancer tissues. Taken together, these results indicate that cyclin D1b expression contributes to the female- specific rectal carcinogenesis in mouse model.

Serrated polyps of the colon: how reproducible is their classification?

For several years, the lack of consensus on definition, nomenclature, natural history, and biology of serrated polyps (SPs) of the colon has created considerable confusion among pathologists. According to the latest WHO classification, the family of SPs comprises hyperplastic polyps (HPs), sessile serrated adenomas/polyps (SSA/Ps), and traditional serrated adenomas (TSAs). The term SSA/P with dysplasia has replaced the category of mixed hyperplastic/adenomatous polyps (MPs). The present study aimed to evaluate the reproducibility of the diagnosis of SPs based on currently available diagnostic criteria and interactive consensus development. In an initial round, H&E slides of 70 cases of SPs were circulated among participating pathologists across Europe. This round was followed by a consensus discussion on diagnostic criteria. A second round was performed on the same 70 cases using the revised criteria and definitions according to the recent WHO classification. Data were evaluated for inter-observer agreement using Kappa statistics. In the initial round, for the total of 70 cases, a fair overall kappa value of 0.318 was reached, while in the second round overall kappa value improved to moderate (kappa = 0.557; p < 0.001). Overall kappa values for each diagnostic category also significantly improved in the final round, reaching 0.977 for HP, 0.912 for SSA/P, and 0.845 for TSA (p < 0.001). The diagnostic reproducibility of SPs improves when strictly defined, standardized diagnostic criteria adopted by consensus are applied.

Serrated polyps: critical precursors to colorectal cancer

Colorectal polyps have been traditionally classified as either hyperplastic or adenomatous, with only the latter progressing to carcinoma. However, it is now recognized that certain subtypes of serrated polyps have a risk of malignant transformation via a serrated neoplasia pathway. Serrated polyps are a heterogeneous group of lesions with distinct morphologic, histologic and molecular genetics profiles. Based on available evidence, there are reasons to suspect that this pathway may contribute to interval or missed cancers because serrated lesions are more likely than conventional adenomas to be missed on colonoscopy, and the progression of serrated polyps to cancer may be more rapid. Therefore, it is paramount that physicians recognize the importance of serrated polyps and are aware of the latest surveillance guidelines.

Endoscopic and surgical management of serrated colonic polyps

BACKGROUND

Serrated polyps are an inhomogeneous group of lesions that harbour precursors of colorectal cancer. Current research has been directed at further defining the histopathological characteristics of these lesions, but definitive treatment recommendations are unclear. The aim was to review the current literature regarding classification, molecular genetics and natural history of these lesions in order to propose a treatment algorithm for surgeons to consider.

METHODS

The PubMed database was searched using the following search terms: serrated polyp, serrated adenoma, hyperplastic polyp, hyperplastic polyposis, adenoma, endoscopy, surgery, guidelines. Papers published between 1980 and 2010 were selected.

RESULTS

Sixty papers met the selection criteria. Most authors agree that recommendations regarding endoscopic or surgical management should be based on the polyp's neoplastic potential. Polyps greater than 5 mm should be biopsied to determine their histology so that intervention can be directed accurately. Narrow-band imaging or chromoendoscopy may facilitate the detection and assessment of extent of lesions. Complete endoscopic removal of sessile serrated adenomas in the left or right colon is recommended. Follow-up colonoscopy is recommended in 2-6 months if endoscopic removal is incomplete. If the lesion cannot be entirely removed endoscopically, segmental colectomy is strongly recommended owing to the malignant potential of these polyps. Left-sided lesions are more likely to be pedunculated, making them more amenable to successful endoscopic removal.

CONCLUSION

Even though the neoplastic potential of certain subtypes of serrated polyp is heavily supported, further studies are needed to make definitive endoscopic and surgical recommendations.

Retained cell–cell adhesion in serrated neoplastic pathway as opposed to conventional colorectal adenomas

The molecular features of serrated polyps of colorectum remain to be elucidated. The expression pattern of adhesive molecules (E-cadherin, α-catenin, and β-catenin) has not been examined in serrated neoplastic pathway. The expression of E-cadherin, α-catenin, and β-catenin were analyzed by immunohistochemistry in 32 hyperplastic polyps (HPs), 28 sessile serrated adenomas (SSAs), 37 traditional serrated adenomas (TSAs), 51 traditional adenomas (TAs), and 10 normal colonic tissues (NCs). Retained membranous expression for E-cadherin, α-catenin, and β-catenin was more frequent in HPs, SSAs, and TSAs than that in TAs (p < 0.001). Nuclear labeling of β-catenin was detected in 19.6% of TAs, but in none of HPs, SSAs, and TSAs (p < 0.001). Cytoplasmic accumulation of β-catenin was found in 3.1% of HPs, 3.6% of SSAs, and 21.6% of TSAs, significantly lower than that in TAs (60.8%, p < 0.001). The membranous co-expression of E-cadherin, α-catenin, and β-catenin was more frequent in HPs (68.8%), SSAs (60.7%), and TSAs (37.8%) than that in TAs (7.8%, p < 0.001). Cell adhesion function is retained in serrated neoplastic pathway. Wnt signaling pathway plays a less active role in the development of colorectal serrated polys than in TAs.

Association between folate levels and CpG Island hypermethylation in normal colorectal mucosa

Gene-specific promoter methylation of several genes occurs in aging normal tissues and may predispose to tumorigenesis. In the present study, we investigate the association of blood folate levels and dietary and lifestyle factors with CpG island (CGI) methylation in normal colorectal mucosa. Subjects were enrolled in a multicenter chemoprevention trial of aspirin or folic acid for the prevention of large bowel adenomas. We collected 1,000 biopsy specimens from 389 patients, 501 samples from the right colon and 499 from the rectum at the follow-up colonoscopy. We measured DNA methylation of estrogen receptor alpha (ERα) and secreted frizzled related protein-1 (SFRP1), using bisulfite pyrosequencing. We used generalized estimating equations regression analysis to examine the association between methylation and selected variables. For both ERα and SFRP1, percentage methylation was significantly higher in the rectum than in the right colon (P = 0.001). For each 10 years of age, we observed a 1.7% increase in methylation level for ERα and a 2.9% increase for SFRP1 (P < 0.0001). African Americans had a significantly lower level of ERα and SFRP1 methylation than Caucasians and Hispanics. Higher RBC folate levels were associated with higher levels of both ERα (P = 0.03) and SFRP1 methylation (P = 0.01). Our results suggest that CGI methylation in normal colorectal mucosa is related to advancing age, race, rectal location, and RBC folate levels. These data have important implications regarding the safety of supplementary folate administration in healthy adults, given the hypothesis that methylation in normal mucosa may predispose to colorectal neoplasia.

Ink4a/Arf and oncogene-induced senescence prevent tumor progression during alternative colorectal tumorigenesis

Colonic cancers with a serrated morphology have been proposed to comprise a molecularly distinct tumor entity following an alternative pathway of genetic alterations independently of APC mutations. We demonstrate that intestinal epithelial cell specific expression of oncogenic K-ras(G12D) in mice induces serrated hyperplasia, which is characterized by p16(ink4a) overexpression and induction of senescence. Deletion of Ink4a/Arf in K-ras(G12D) expressing mice prevents senescence and leads to invasive, metastasizing carcinomas with morphological and molecular alterations comparable to human KRAS mutated serrated tumors. Thus, we suggest that oncogenic K-ras represents a key player during an alternative, serrated pathway to colorectal cancer and hence propose RAS-RAF-MEK signaling apart from APC as an additional gatekeeper in colorectal tumor development.

Serrated adenoma: a distinct form of non-polypoid colorectal neoplasia?

Until recently, 2 major forms of colorectal polyp were recognized: the adenoma and the hyperplastic polyp. Adenomas were known to represent a precursor to colorectal cancer, whereas hyperplastic polyps were viewed as nonneoplastic, having no potential for progression to malignancy. We now recognize, however, that the lesions diagnosed as hyperplastic polyps in the past represent a heterogeneous group of polyps, some of which truly are hyperplastic, and others that truly have a significant risk for transformation to colorectal cancer. These polyps have a characteristic serrated architecture, and include not only hyperplastic polyps but also the recently recognized serrated adenomas. Serrated adenomas occur in 2 forms: the traditional serrated adenoma, which is usually a polypoid lesion endoscopically, and the sessile serrated adenoma, a flat or slightly raised, usually right-sided lesion. Serrated adenomas of both types show characteristic molecular alterations not commonly seen in traditional colorectal adenomas, and probably progress to colorectal cancer by means of a different pathway, the so-called serrated neoplasia pathway. The morphologic features of serrated colorectal lesions, the molecular alterations that characterize them, and their role in colorectal cancer development are discussed.

The association of lifestyle and dietary factors with the risk for serrated polyps of the colorectum

Some serrated polyps of the colorectum are likely preinvasive lesions, evolving through a newly recognized serrated pathway to colorectal cancer. To assess possible risk and protective factors for serrated polyps and particularly to explore differences in risk factors between polyps in the right and left colorectum, we pooled data from three large multicenter chemoprevention trials. A serrated polyp was defined broadly as any serrated lesion (hyperplastic, sessile serrated adenoma, "traditional" serrated adenoma, mixed adenoma) diagnosed during each trial's main treatment period of approximately 3 to 4 years. Using generalized linear regression, we computed risk ratios and 95% confidence intervals as measures of the association between risk for serrated polyps and demographic, lifestyle, and dietary variables. Of the 2,830 subjects that completed at least one follow-up exam after randomization, 675 (23.9%) had at least one left-sided serrated polyp and 261 (9.2%) had at least one right-sided lesion. In the left colorectum, obesity, cigarette smoking, dietary fat, total energy intake, and red meat intake were associated with an increased risk for serrated polyps. In the right colon, aspirin treatment was associated with a reduced risk and family history of polyps and folate treatment were associated with an increased risk for serrated polyps. Our results suggest that several common lifestyle and dietary variables are associated with risk for serrated polyps, and some of these may differ for the right and left colorectum.

Reinterpretation of histology of proximal colon polyps called hyperplastic in 2001

AIM: To evaluate how proximal colon polyps interpreted as hyperplastic polyps in 2001 would be interpreted by expert pathologists in 2007.

METHODS: Forty consecutive proximal colon polyps ≥ 5 mm in size, removed in 2001, and originally interpreted as hyperplastic polyps by general pathologists at Indiana University, were reviewed in 2007 by 3 GI pathologists.

RESULTS: The gastrointestinal (GI) pathologists interpreted 85%, 43% and 30% of the polyps as sessile serrated polyps (sessile serrated adenomas). The overall Kappa was 0.16. When diagnoses were compared in pairs, Kappa values were 0.38 and 0.25 (fair agreement) and 0.14 (slight agreement).

CONCLUSION: Many polyps interpreted as hyperplastic in 2001 were considered sessile serrated lesions by GI pathologists in 2007, but there is substantial inter-observer variation amongst GI pathologists.

Serrated polyps and colorectal cancer: new pathway to malignancy

Until recently, two major forms of colorectal epithelial polyp were recognized: the adenoma and the hyperplastic polyp. Adenomas were perceived to represent the precursor to colorectal cancer, whereas hyperplastic polyps were viewed as innocuous lesions with no potential for progression to malignancy. We now recognize, however, that the lesions formerly classified as hyperplastic actually represent a heterogeneous group of polyps, some of which have a significant risk for neoplastic transformation. These serrated polyps include not only hyperplastic polyps but also traditional serrated adenomas and sessile serrated adenomas. These polyps demonstrate characteristic molecular alterations not commonly seen in colorectal adenomas, and they probably progress to colorectal cancer by means of a new pathway: the serrated neoplasia pathway. The morphologic features of serrated colorectal lesions, the molecular alterations that characterize them, and their role in colorectal cancer development are discussed herein.

Narrow-band imaging without high magnification to differentiate polyps during real-time colonoscopy: improvement with experience

BACKGROUND

There is no widely adopted, easily applied method for distinguishing between adenomatous and nonadenomatous polyps during real-time colonoscopy.

OBJECTIVE

To compare white light (WL) with narrow-band imaging (NBI) for the differentiation of colorectal polyps in vivo and to assess for a learning curve.

DESIGN

A prospective polyp series.

PATIENTS AND SETTING

A total of 302 patients referred for colonoscopy, between August 2006 and July 2007, to a single tertiary-referral center in the United States.

INTERVENTION

Standard WL colonoscopy was performed with Olympus 180-series colonoscopes. Each detected polyp was first characterized by WL and then by NBI. Modified Kudo pit pattern and vascular color intensity (VCI) were recorded, and the histology was predicted. Endoscopists were given feedback every 2 weeks.

MAIN OUTCOME MEASUREMENTS

Overall accuracy and sensitivity and specificity of endoscopic diagnosis by using WL alone and with NBI, as well as improvement in endoscopists' performance.

RESULTS

A total of 265 polyps were found in 131 patients. Diagnostic accuracy was 80% with NBI and 77% with WL (P = .35). NBI performed better than WL in diagnosing adenomas (sensitivity 80% vs 69%, P < .05). Nonadenomatous polyps were more likely to have a "light" VCI compared with adenomas (71% vs 29%, P < .001). During the second half of the study, NBI accuracy improved, from 74% to 87%, and outperformed an unchanged WL accuracy of 79% (P < .05).

CONCLUSIONS

Overall, NBI was not more accurate than WL in differentiating colorectal polyps in vivo; however, once a learning curve was achieved, NBI performed significantly better. Further refinements of an NBI pit-pattern classification and VCI scale are needed before broad application to clinical decisions regarding the necessity of polypectomy.

The case for a genetic predisposition to serrated neoplasia in the colorectum: hypothesis and review of the literature

In recent years, an alternative pathway of colorectal cancer development has been described in which serrated polyps replace the traditional adenoma as the precursor lesion. Importantly, serrated polyps and a subset of colorectal cancer show largely nonoverlapping mutation profiles to those found in adenomas and the majority of colorectal cancer. These genetic alterations include activating mutation of the BRAF proto-oncogene and widespread gene promoter hypermethylation (CpG island methylator phenotype or CIMP). Up to 15% of colorectal cancer is likely to develop on the basis of a strong genetic predisposition. The two most well-characterized syndromes, familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer (Lynch syndrome), both develop via the adenoma-carcinoma pathway and together account for approximately one third of familial colorectal cancer. We have recently described 11 families in which there is evidence that the genetic predisposition to autosomal dominant colorectal cancer is linked to the serrated pathway. This condition, serrated pathway syndrome, and the related condition, hyperplastic polyposis, the presentation of which suggests a recessive mode of inheritance, represent two syndromes in which BRAF mutation and methylation co-occur within serrated precursor lesions. Further, CIMP is observed in the normal colonic mucosa of individuals with hyperplastic polyposis consistent with a field defect in epigenetic regulation. The spectrum of serrated neoplasia may also implicate the apparently sporadic and later onset subset of colorectal cancer with high levels of microsatellite instability. The tendency for these lesions to be multiple, associated with smoking, and to show frequent BRAF mutation and CIMP points to a defect that may result from interactions between the environment and a weakly penetrant genetic alteration.

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

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

Colorectal serrated adenocarcinoma

Colorectal cancer (CRC) ranks among the three most common cancers in terms of both cancer incidence and cancer-related deaths in most Western countries. Serrated adenocarcinoma is a recently described, distinct variant of CRC, accounting for about 7.5% of all CRCs and up to 17.5% of most proximal CRCs. It has been postulated that about 10-15% of sporadic CRCs would have their origin in serrated polyps that harbour a significant malignant potential. These lesions include hyperplastic-type aberrant crypt foci, hyperplastic polyps, sessile serrated adenomas, admixed polyps and serrated adenomas, and constitute the so-called 'serrated pathway', which is distinct from both the conventional adenoma-carcinoma pathway and the mutator pathway of hereditary non-polyposis CRC and is characterized by early involvement of oncogenic BRAF mutations, excess CpG island methylation (CIM) and subsequent low- or high-level DNA microsatellite instability (MSI). Methylation of hMLH1 is likely to explain the increased frequency of high-level MSI (16%) and methylation of MGMT is postulated to explain the low-level MSI (29%) in serrated adenocarcinomas. Reproducible histopathological criteria for serrated adenocarcinoma have recently been established and they have been qualified by DNA expression analysis for 7928 genes, showing clustering of serrated adenocarcinomas into a molecular entity apart from conventional adenocarcinoma, and representing with distinct down-regulation of EPHB2, PTCH and up-regulation of HIF1alpha.

Sessile serrated adenoma is associated with acute appendicitis in patients 30 years or older

Sessile serrated adenoma is a relatively recently described entity that can occur in the appendix. The incidence of this finding is unknown. We entirely submitted 100 consecutive appendices sent for acute appendicitis and correlated the histologic findings with clinical parameters and the findings in 100 routinely (partially) submitted cases. In cases submitted routinely, only 1 sessile serrated adenoma was found. In contrast, in cases entirely submitted, 11 adenomas were found, all in patients 30 years or older. All sessile serrated adenomas were present in 3 cross-sections or fewer of the appendix. The incidence of sessile serrated adenoma in patients with acute appendicitis is significantly increased in patients 30 years or older (P = .001), and detection is dependent on thorough tissue sampling.

New insights into the molecular pathogenesis of colorectal cancer

Although there have been tremendous advances in the management of colorectal cancer (CRC), there is still a need for improved therapeutic approaches. On a molecular genetic level, CRC is one of the best-understood solid malignancies, and these insights can serve as a foundation for the design of novel targeted therapies. We present new genetic and epigenetic pathways that highlight the heterogeneous mechanisms in CRC pathogenesis, including the roles of the MYH DNA repair gene and of aberrant DNA hypermethylation and imprinting. We then describe some of the successful targeted therapies that inhibit COX2, EGFR, and VEGF as well as potential new targets that have been revealed by studies of molecular genetics.