Identification of histologically distinct conventional adenomas that arise predominately in patients with sessile serrated adenomas

The Second Allele: A Key to Understanding the Timing of Sporadic and Hereditary Colorectal Tumorigenesis

Our understanding of the molecular basis of colorectal neoplasia is derived from Mendelian genetics, with tumor suppressor genes contributing more to the deregulation of growth than oncogenes. In patients with hereditary syndromes, expression of one allele of a key tumor suppressor gene is absent at birth. The loss of the expression of the second allele precipitates tumorigenesis. However, there are multiple ways in which the expression of the second allele of a tumor suppressor gene is lost. Here, we review these ways and their possible effect on phenotype.

RNF43 pathogenic Germline variant in a family with colorectal cancer

The role of RNF43 as a cause of an inherited predisposition to colorectal cancer (CRC) is yet to be fully explored. This report presents our findings of two individuals with CRC from a single family carrying a likely-pathogenic inherited germline variant in RNF43. The proband (III:1) and the proband's mother (II:2) were diagnosed with mismatch repair proficient CRCs at the age of 50 years and 65 years, respectively. Both patients had BRAF^V600E mutated colon tumours, indicating that the CRCs arose in sessile serrated lesions. The germline variant RNF43:c.375+1G>A was identified in both patients. RNA studies showed that this variant resulted in an aberrantly spliced transcript, which was predicted to encode RNF43:p.Ala126Ilefs*50 resulting in premature termination of protein synthesis and was classified as a likely-pathogenic variant. Our report adds further evidence to the hereditary role of RNF43 as a tumour suppressor gene in colorectal tumorigenesis and supports the inclusion of RNF43 as a gene of interest in the investigation of CRC predispositions outside the setting of serrated polyposis.

Patterns of polyp histology: predictors of peril in the mucosa

BACKGROUND

Precursor colonic polyps of varied subtypes correlate with the known neoplastic pathways. When patients present with synchronous pre-malignant polyps of multiple histologies, multiple genetic mechanisms are likely to be active, potentially resulting in a more unstable, tumourigenic mucosa.

METHODS

We hypothesized that patients with a combination of sessile serrated adenomas/polyps (SSA/Ps), hyperplastic (HP) polyps and adenomas would be at highest risk of developing dysplasia/cancer compared to SSA/Ps alone, due to the synergistic effect of multiple active carcinogenic pathways. A prospective colonoscopy database was examined for patients with a history of SSA/P. Patients were placed into four groups based on patterns of polyp histology as follows: (i) only SSA/Ps; (ii) SSA/P + HP; (iii) SSA/Ps + adenomas; and (iv) SSA/Ps + HP + adenomas. These groups were compared in terms of the numbers, size, location and histology of polyps and personal or family history of colorectal cancer.

RESULTS

A total of 374 patients were included. The average age was 70 years (range 21-88), and 43% were male. There was a trend towards the most aggressive neoplastic pattern in group 4, associated with a tendency to larger SSA/Ps, more villous architecture in the adenomas and more high-grade dysplasia in both types of polyps. It was also associated with multiplicity of both SSA/Ps and adenomas. No SSA/Ps existing in the absence of adenomas had cytological dysplasia.

CONCLUSION

The combination of SSA/Ps, HP and adenomas in the colorectal epithelium seems to be a marker for aggressive carcinogenesis and suggests that accurate and effective surveillance is important to manage this risk.

Sessile Serrated Polyposis: Not an Inherited Syndrome?

BACKGROUND

Researchers are searching in vain for a coherent genetic explanation for serrated polyposis. We hypothesize that there is no consistent monogenetic inheritance.

OBJECTIVE

The purpose of this study was to describe the serrated polyposis phenotype, assessing features of mendelian inheritance, and to compare these features with patients with a solitary sessile serrated lesion.

DESIGN

This was a retrospective review of a prospectively maintained database comparing patients with serrated polyposis versus solitary sessile serrated lesions.

SETTINGS

The study was conducted at a single-institution tertiary referral center.

PATIENTS

Patients with serrated polyposis meeting World Health Organization criteria type I (≥5 serrated polyps proximal to the sigmoid, ≥2 of which are ≥10 mm in diameter) and isolated sessile serrated lesions were included MAIN OUTCOME MEASURES:: Disease phenotype was the main outcome measured.

RESULTS

A total of 46 serrated polyposis patients were identified. Median age of first sessile serrated lesion was 66 years (interquartile range, 42-70 y). A total of 60.3% were current or past smokers (mean = 38.6 packs per year). Serrated polyposis patients had a higher number of all types of polyps (26.3 vs 4.4) and a higher rate of high-grade dysplasia (19.6% vs 3.7%) compared with patients with a solitary sessile serrated lesion. A total of 36.2% of patients had personal history of noncolorectal cancers, including skin, prostate, breast, thyroid, and renal cell cancers and leukemia. In addition, 32.6% had a family history of colorectal cancer in first- or second-degree relatives; these cancers were not young age of onset. Breast and prostate cancers were also common (family history of any cancer, 83.0%). Ten patients underwent genetic testing: 4 had negative panels, 1 had a pathogenic variant in MSH2, 1 an IVS7 deletion in PTEN, 2 negative APC sequencing (1 negative MYH), and 1 a pathogenic variant in Chek2.

LIMITATIONS

RNF4 was not sequenced. Genetic analysis was performed on a subset of patients.

CONCLUSIONS

The rate of associated cancers suggests an underlying genetic predisposition to disordered growth, but serrated polyposis does not have typical features of dominant inheritance. The association with smoking suggests that familial/environmental factors play a role. See Video Abstract at http://links.lww.com/DCR/B84. POLIPOSIS SERRADA SÉSIL: ¿NO ES UN SÍNDROME HEREDITARIO?: Los investigadores están buscando en vano una explicación genética coherente para la póliposis serrados. Suponemos que no existe una herencia monogenética consistente.1) Describir el fenotipo de póliposis serrada, evaluando las características de la herencia mendeliana, 2) comparar estas características con pacientes con una lesión serrada sésil solitaria.Revisión retrospectiva de una base de datos mantenida prospectivamente que compara pacientes con póliposis serrada versus lesiones serradas sésiles solitarias.Institución única, centro de referencia terciario.Pacientes con póliposis serrada que cumplen con los Criterios de la Organización Mundial de la Salud Tipo I (≥ 5 pólipos serrados proximales al sigmoideo, ≥2 de los cuales tienen ≥10 mm de diámetro) y lesiones serradas sésiles aisladas.Fenotipo de la enfermedad.Se identificaron un total de 46 pacientes con póliposis serrada. La edad mediana de la primera lesión serrada sésil fue de 66 años (RIC: 42-70 años). El 60.3% eran fumadores actuales o pasados (medio 38.6 paquetes / año). Los pacientes con póliposis serrada tuvieron un mayor número de todos los tipos de pólipos (26.3 versus 4.4) y una mayor tasa de displasia de alto grado (19.6% versus 3.7%) en comparación con los pacientes con una lesión serrada sésil solitaria. El 36.2% de los pacientes tenían antecedentes personales de cánceres no colorectales, incluyendo los cánceres de piel, próstata, mama, tiroides, células renales y leucemia. El 32.6% tenía antecedentes familiares de cáncer colorectal en familiares de primer o segundo grado; estos cánceres no eran de inicio de edad temprana. El cáncer de mama y próstata también fue frecuente (antecedentes familiares de cualquier tipo de cáncer: 83.0%). 10 pacientes se sometieron a pruebas genéticas: 4 tenían paneles negativos, 1 tenía una variante patogénica en MSH2, 1 una eliminación IVS7 en PTEN, 2 secuenciación APC negativa (1 MYH negativa) y 1 variante patogénica en Chek2.RNF4 no fue secuenciado. El análisis genético se realizó en un subconjunto de pacientes.La tasa de cánceres asociados sugiere una predisposición genética subyacente al crecimiento desordenado, pero la póliposis serrada no tiene características típicas de herencia dominante. La asociación con el tabaquismo sugiere que los factores familiares / ambientales juegan un papel. Consulte Video Resumen en http://links.lww.com/DCR/B84. (Traducción-Dr. Yesenia Rojas-Khalil).

Sessile Serrated Polyps with Synchronous Conventional Adenomas Increase Risk of Future Advanced Neoplasia

BACKGROUND

Surveillance colonoscopy guidelines following adenomas or sessile serrated adenomas/polyps (SSPs) are based on pathology features known to be associated with risk of future colorectal cancer. A synchronous conventional adenoma may increase the malignant potential of SSP, but current guidelines do not address this combination of pathologies.

AIMS

The aim was to assess the risk of advanced neoplasia after SSP with or without synchronous adenoma compared to that following a conventional adenoma.

METHODS

An audit was conducted on colonoscopies performed between 2000 and 2014 as part of a surveillance program. Index colonoscopy findings were classified as: low-risk SSP and high-risk SSP (size ≥ 10 mm or with cytological dysplasia) with and without synchronous adenoma; high-risk adenoma and low-risk adenoma. Risk of advanced neoplasia was determined at subsequent surveillance colonoscopies.

RESULTS

In total, 2157 patients had adenoma or SSP found at index colonoscopy-low-risk adenoma (40%), high-risk adenoma (54%) and SSP (4%). Synchronous adenomas were seen with 47% of SSP. The median follow-up was 50.3 months (interquartile range 28.1-79.3). Compared to an index finding of low-risk adenoma, index findings of high-risk adenoma, as well as SSP with synchronous adenoma, were independent predictors of future advanced neoplasia (high-risk adenoma: hazard ratio (HR) = 2.04 (95% CI 1.70-2.45); high-risk SSP + adenoma HR = 3.20 (95% CI 1.31-7.82); low-risk SSP + adenoma: HR = 2.20 (95% CI 1.03-4.68)).

CONCLUSIONS

Synchronous adenoma increases the risk of advanced neoplasia for SSP equivalent to that seen following high-risk adenoma. Guidelines for surveillance should take into account concurrent pathologies with SSP.

Aspects of the Natural History of Sessile Serrated Adenomas/Polyps: Risk Indicators for Carcinogenesis in the Colorectal Mucosa?

BACKGROUND

Sessile serrated adenomas/polyps are potentially premalignant colorectal lesions that are precursors to colorectal cancer arising via CpG island methylator phenotype. They are caused by the combination of a BRAF mutation and promoter hypermethylation. DNA methylation is an age-dependent phenomenon in the right colon, and we would expect the occurrence and severity of serrated neoplasia to reflect this.

OBJECTIVE

The purpose of this study was to document the natural history of sessile serrated adenomas/polyps, including the ages at which they appear and the ranges of their number, size, and associated lesions.

DESIGN

This was a retrospective cohort study.

SETTINGS

The study was conducted at a tertiary referral center.

PATIENTS

Consecutive patients with sessile serrated adenomas/polyps removed between 2006 and 2015 were included. Patients with IBD, familial adenomatous polyposis, Lynch syndrome, serrated polyposis, and hereditary nonpolyposis colorectal cancer were excluded.

MAIN OUTCOME MEASURES

Age at which polyps were first diagnosed, location and size of polyps, demographics, and family history were measured.

RESULTS

A total of 440 patients had 668 sessile serrated adenomas/polyps, 257 (58%) also had ≥1 adenoma, and 28 (6%) had a history of colorectal cancer. Mean age at diagnosis was 68 ± 11 years, and 45% were men. Two hundred had had ≥1 colonoscopy before the diagnosis of the first sessile serrated adenomas/polyps. A total of 136 patients (31%) had multiple sessile serrated adenomas/polyps, including 24% synchronous and 10% metachronous. The range of total cumulative sessile serrated adenomas/polyps was from 1 to 7. A total of 554 (83%) of 668 sessile serrated adenomas/polyps were right sided; 48% were ≥1 cm diameter and 22% were >2 cm. The size of the first sessile serrated adenomas/polyps in those diagnosed under age 50 years averaged 10 mm, those between 50 and 60 years averaged 12 mm, and those between 60 and 70 years averaged 12 mm.

LIMITATIONS

No measurement of methylation or BRAF mutations in polyps or normal mucosa and a lack of subclassification of hyperplastic polyps limited this study.

CONCLUSIONS

The age of onset of sessile serrated adenomas/polyps varies, but the pattern is consistent with increasing methylation in the mucosa. Early negative colonoscopies predict a low risk of methylator cancers. See Video Abstract at http://links.lww.com/DCR/A736.

Findings in young adults at colonoscopy from a hospital service database audit

BACKGROUND

Colorectal cancer (CRC) diagnosed at <50 years is predominantly located in the distal colon and rectum. Little is known about which lesion subtypes may serve as CRC precursors in young adults. The aim of this work was to document the prevalence and histological subtype of lesions seen in patients aged <50 years, and any associated clinical features.

METHODS

An audit of the colonoscopy database at The Queen Elizabeth Hospital in Adelaide, South Australia over a 12-month period was undertaken. Findings were recorded from both colonoscopy reports and corresponding histological examination of excised lesions.

RESULTS

Data were extracted from colonoscopies in 2064 patients. Those aged <50 comprised 485 (24%) of the total. CRC precursor lesions (including sessile serrated adenoma/polyps (SSA/P), traditional serrated adenomas, tubular adenomas ≥10 mm or with high-grade dysplasia, and conventional adenomas with villous histology) were seen in 4.3% of patients aged <50 and 12.9% of patients aged ≥50 (P <0.001). Among colonoscopies yielding CRC precursor lesions in patients under 50 years, SSA/P occurred in 52% of procedures (11/21), compared with 27% (55/204) of procedures in patients aged 50 and older (P = 0.02). SSA/P were proximally located in (10/11) 90% of patients aged under 50, and 80% (43/54) of those aged 50 and older (P = 0.46).

CONCLUSIONS

SSA/P were the most frequently observed CRC precursor lesions in patients aged <50. Most CRCs in this age group are known to arise in the distal colon and rectum suggesting that lesions other than SSA/P may serve as the precursor for the majority of early-onset CRC.

The molecular characteristics of colonic neoplasms in serrated polyposis: a systematic review and meta-analysis

Serrated polyposis is a rare disorder characterised by the presence of multiple serrated polyps in the large intestine, and an increased personal and familial risk of colorectal cancer. Knowledge of the molecular characteristics of colonic lesions which develop in this syndrome is fragmented, making it difficult to understand the underlying genetic basis of this condition. We conducted a systematic review and meta-analysis of all studies which evaluated the molecular characteristics of colorectal neoplasms found in individuals with serrated polyposis. We identified 4561 potentially relevant studies, but due to a lack of consensus in the reporting of findings, only fourteen studies were able to be included in the meta-analysis. BRAF mutation was found in 73% (95% CI 65-80%) of serrated polyps, 0% (95% CI 0-3%) of conventional adenomas and 49% (95%CI 33-64%) of colorectal cancers. In contrast, KRAS mutation was present in 8% (95% CI 5-11%) of serrated polyps, 3% (95% CI 0-13%) of conventional adenomas and 6% (95% CI 0-13%) of colorectal cancers. Absence of MLH1 immunostaining was found in 3% (95% CI 0-10%) of serrated polyps and 53% (95% CI 36-71%) of colorectal cancers. Overall, microsatellite instability was found in 40% (95% CI 18-64%) of colorectal cancers arising in the setting of serrated polyposis. Our results indicate that diverse molecular pathways are likely to contribute to the increased predisposition for colorectal cancer in individuals with serrated polyposis. We also propose a set of minimum standards for the reporting of future research in serrated polyposis as this is a rare syndrome and collation of research findings from different centres will be essential to identify the molecular mechanisms involved in the pathogenesis of this condition.

Inflammatory response in serrated precursor lesions of the colon classified according to WHO entities, clinical parameters and phenotype-genotype correlation

Studies on traditional serrated adenoma (TSA) and sessile serrated adenoma with dysplasia (SSA‐D) are rare due to the low frequency of these lesions, which are well defined by the latest WHO classification. However, introducing new morphological criteria such as intra‐epithelial lymphocytes (IELs) might facilitate colorectal polyp diagnoses. Additionally, the phenotype–genotype correlation needs to be updated as the terminology has repeatedly changed. This study analysed 516 polyps, consisting of 118 classical adenomas (CAD), 116 hyperplastic polyps (HPP), 179 SSAs, 41 SSA‐Ds, and 62 TSAs. The lesions were analysed in relation to the patients’ clinical parameters including gender, age, localisation, and size. The inflammatory background of the polyps was quantified and BRAF and KRAS mutations as well as MLH1 and CDKN2A promoter methylation were assessed. In multivariate analyses, an increase in IELs was an independent and robust new criterion for the diagnosis of SSA‐D (p < 0.001). Superficial erosions and acute neutrophil granulocytes led to reactive changes potentially resembling dysplasia. KRAS and BRAF mutations were associated with CAD/TSA and HPP/SSA, respectively. However, almost half of TSAs had a BRAF mutation and were KRAS wild type. CDKN2A seems to precede MLH1 hyper‐methylation within the serrated carcinogenesis model. The genotyping of WHO‐based entities – and especially SSA – has sharpened in comparison to previously published data. TSAs can be sub‐grouped according to their mutation status. Of note, the higher number of IELs in SSA‐D reflects their close relationship to colorectal cancers with micro‐satellite instability. Therefore, IELs might represent a new diagnostic tool for SSA‐D.

Serrated tubulovillous adenoma of the large intestine

AIMS

Most colorectal polyps are classified readily, but a subset of tubulovillous adenomas (TVA) with prominent serrated architecture causes diagnostic confusion. We aimed to (i) identify histological features that separate serrated TVAs from both conventional TVAs and traditional serrated adenomas (TSA) and (ii) perform a clinicopathological and molecular analysis to determine if the serrated TVA has unique features.

METHODS AND RESULTS

We collected 48 serrated TVAs, 50 conventional TVAs and 66 BRAF wild-type TSAs for analysis. For each polyp we performed a clinicopathological assessment, BRAF and KRAS mutation profiling, cytosine-phosphate-guanosine (CpG) island methylator phenotype status, MGMT methylation and immunohistochemical assessment of seven markers [MutL homologue 1 (MLH1), p16, p53, β-catenin, Ki67, CK7 and CK20]. We found that serrated TVAs can be diagnosed reliably, and have features distinct from both conventional TVAs and TSAs. Compared to conventional TVAs, serrated TVAs are larger, more often proximal, more histologically advanced, show more CpG island methylation and more frequent KRAS mutation. Compared to TSAs they are more often proximal, show less CpG island methylation, more frequent MGMT methylation and more frequent nuclear staining for β-catenin.

CONCLUSIONS

The serrated TVA can be diagnosed reliably and has unique features. It represents a precursor of KRAS mutated, microsatellite stable colorectal carcinoma.

Long-term risk of colorectal cancer in individuals with serrated polyps

OBJECTIVE

Although serrated polyps may be precursors of colorectal cancer (CRC), prospective data on the long-term CRC risk in individuals with serrated polyps are lacking.

DESIGN

In a population-based randomised trial, 12,955 individuals aged 50-64 years were screened with flexible sigmoidoscopy, while 78 220 individuals comprised the control arm. We used Cox models to estimate HRs with 95% CIs for CRC among individuals with ≥1 large serrated polyp (≥10 mm in diameter), compared with individuals with adenomas at screening, and to population controls, and multivariate logistic regression to assess polyp risk factors for CRC.

RESULTS

A total of 103 individuals had large serrated polyps, of which 81 were included in the analyses. Non-advanced adenomas were found in 1488 individuals, advanced adenomas in 701. Median follow-up was 10.9 years. Compared with the control arm, the HR for CRC was 2.5 (95% CI 0.8 to 7.8) in individuals with large serrated polyps, 2.0 (95% CI 1.3 to 2.9) in individuals with advanced adenomas and 0.6 (95% CI 0.4 to 1.1) in individuals with non-advanced adenomas. A large serrated polyp was an independent risk factor for CRC, adjusted for histology, size and multiplicity of concomitant adenomas (OR 3.3; 95% CI 1.3 to 8.6). Twenty-three large serrated polyps found at screening were left in situ for a median of 11.0 years. None developed into a malignant tumour.

CONCLUSIONS

Individuals with large serrated polyps have an increased risk of CRC, comparable with individuals with advanced adenomas. However, this risk may not be related to malignant growth of the serrated polyp.

TRIAL REGISTRATION NUMBER

The Norwegian Colorectal Cancer Screening trial is registered at clinicaltrials.gov (NCT00119912).

Serrated polyps and the risk of synchronous colorectal advanced neoplasia: a systematic review and meta-analysis

OBJECTIVES

Serrated polyps of the colon comprise a heterogeneous group of lesions with distinct histological and malignant features. The presence of serrated polyps has been associated with synchronous advanced neoplasia, although the magnitude of this relationship is unclear.

METHODS

Using studies identified from systematic literature search up to February 2014, we performed a systematic review and meta-analysis to estimate the pooled prevalence of serrated polyps and their association with synchronous advanced neoplasia. Random-effects models were used to combine estimates from heterogeneous studies, and odds ratios (ORs) with 95% confidence intervals (CIs) were presented.

RESULTS

Nine studies with 34,084 participants were included. The mean age of subjects was 59.9±6.6 years and 52.5% of the subjects were male. Pooled prevalence of serrated polyps was 15.6% (95% CI, 10.3-22.9%). The pooled OR of advanced neoplasia in individuals with serrated polyps was 2.05 (95% CI, 1.38-3.04). Pooled analysis showed that the presence of proximal serrated polyps (OR=2.77, 95% CI, 1.71-4.46) and large serrated polyps (OR=4.10, 95% CI, 2.69-6.26) was associated with an increased risk of synchronous advanced neoplasia. The pooled OR for advanced neoplasia in individuals with proximal and large serrated polyps was 3.35 (95% CI, 2.51-4.46). Considerable heterogeneity was observed in most analyses.

CONCLUSIONS

Our meta-analysis showed that serrated polyps are associated with a more than twofold increased risk of detection of synchronous advanced neoplasia. Individuals with proximal and large serrated polyps have the highest risk. These individuals deserve surveillance colonoscopy.

The significance of ectopic crypt formation in the differential diagnosis of colorectal polyps

Background

Ectopic crypts, defined as abnormally positioned crypts that have lost their orientation toward the muscularis mucosae, have been suggested to be the best defining histologic feature of traditional serrated adenoma (TSA). However, the significance of ectopic crypt formation (ECF) in the distinction between TSA and conventional adenoma (CA) has rarely been studied.

Methods

We designed this study to determine if ECF can be found in CA and its presence is exclusive to TSA. We studied 107 TSAs and 191 CAs including 106 tubular adenomas (TAs), 66 tubulovillous adenomas (TVAs), and 19 villous adenomas (VAs).

Results

ECF was identified in most (79.4%) but not all TSAs. Additionally, ECF was not infrequent in CA (62 of 191, 32.5%), and its presence correlated with the presence of a villous component and larger tumor size (each p <0.001).

Conclusions

Based on its strong association with the presence of a villous component and larger tumor size, ECF appears to be involved in the protuberant growth of colorectal CA. Because ECF can be found in CA, particularly in cases with a villous component, the possibility of CA should be considered before making a diagnosis of TSA when encountering colorectal polyps with ECF.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_212

Histological overlap between colorectal villous/tubulovillous and traditional serrated adenomas

AIMS

To ascertain the degree of histological overlap between conventional villous/tubulovillous (VA/TVAs) and traditional serrated adenomas (TSA).

METHODS AND RESULTS

A total of 180 polyps from the left colon/rectum diagnosed as VA/TVAs were retrieved randomly and reviewed by five pathologists looking specifically at luminal serration, cytoplasmic eosinophilia and the presence of ectopic crypt foci (ECF). For comparative purposes, 100 tubular adenomas and 80 TSAs were also examined. Twenty VA/TVAs were reclassified as TSA. Luminal serration as noted in TSA was not seen in any of the remaining 160 polyps, ECFs were noted in 55 of the 160 VA/TVAs (34%), while cytoplasmic eosinophilia (constituting <50% of the adenoma) was noted in only 10 of 160 cases (6.2%).

CONCLUSIONS

Ectopic crypt foci and cytoplasmic eosinophilia are encountered in sporadic VA/TVAs but not to the same extent and degree as in TSA. ECFs were found in one-third of cases, but cytoplasmic eosinophilia is rare. The pattern of luminal serration in TSA is very characteristic and not recapitulated in VA/TVA. The occurrence of all three histological features together occurs only in TSA. ECFs are not a sine qua non for TSA and are encountered commonly in VA/TVAs. VA/TVAs often contain occasional glands typical of TSA.

Morphologic and molecular characterization of traditional serrated adenomas of the distal colon and rectum

Of the serrated polyps, the origin, morphologic features, molecular alterations, and natural history of traditional serrated adenomas (TSAs) are the least understood. Recent studies suggest that these polyps may arise from precursor lesions. The frequencies of KRAS and BRAF mutations vary between these studies, and only 1 small study has measured CpG island methylation using current markers of methylation. Mutations in GNAS, a gene commonly mutated in colorectal villous adenomas, have not been fully evaluated in TSAs. Finally, the expression of annexin A10 (ANXA10), a recently discovered marker of sessile serrated adenomas/polyps, has not been studied in these polyps. To further characterize these polyps, 5 gastrointestinal pathologists reviewed 55 left-sided polyps diagnosed as TSA at a single institution. Pathologists assessed various histologic features including cytoplasmic eosinophilia, ectopic crypt foci, presence of conventional dysplasia, and presence of precursor serrated lesions. KRAS, BRAF, and GNAS mutational analysis was performed, as well as CpG island methylation and ANXA10 immunohistochemistry. Ectopic crypt foci were seen in 62% of TSAs. Precursor lesions were seen in 24% of the study polyps, most of which were hyperplastic polyps. KRAS and BRAF mutations were common and were present in 42% and 48% of polyps, respectively. GNAS mutations occurred in 8% of polyps, often in conjunction with a BRAF mutation. Unlike sessile serrated adenomas/polyps, TSAs rarely had diffuse expression of ANXA10. Importantly, BRAF-mutated TSAs had more widespread methylation of a 5-marker CpG island panel compared with KRAS-mutated polyps. However, ectopic crypt foci, a proposed defining feature of TSA, were not associated with any specific molecular alteration.

The CIMP Phenotype in BRAF Mutant Serrated Polyps from a Prospective Colonoscopy Patient Cohort

Colorectal cancers arising via the serrated pathway are often associated with BRAF V600E mutation, CpG island methylator phenotype (CIMP), and microsatellite instability. Previous studies have shown a strong association between BRAF V600E mutation and serrated polyps. This study aims to evaluate CIMP status of all the serrated polyp subtypes and its association with functionally important genes such as MLH1, p16, and IGFBP7. CIMP status and methylation were evaluated using the real-time based MethyLight assay in 154 serrated polyps and 63 conventional adenomas. Results showed that CIMP-high serrated polyps were strongly associated with BRAF mutation and proximal colon. CIMP-high was uncommon in conventional adenomas (1.59%), occurred in 8.25% of hyperplastic polyps (HPs), and became common in sessile serrated adenomas (SSAs) (51.43%). MLH1 methylation was mainly observed in the proximal colon and was significantly associated with BRAF mutation and CIMP-high. The number of samples methylated for p16 and IGFBP7 was the highest in SSAs. The methylation panel we used to detect CIMP is highly specific for CIMP-high cancers. With this panel, we demonstrate that CIMP-high is much more common in SSAs than HPs. This suggests that CIMP-high correlates with increased risk of malignant transformation which was also observed in methylation of functionally important genes.

Multiplicity and molecular heterogeneity of colorectal carcinomas in individuals with serrated polyposis

Serrated polyposis (SP) is a clinically defined syndrome characterized by the occurrence of multiple serrated polyps in the large intestine. Individuals with SP and their relatives are at increased risk of colorectal carcinoma (CRC). We aimed to determine the pathologic and molecular profiles of CRCs in individuals fulfilling World Health Organization criteria for SP. A total of 45 CRCs were obtained from 38 individuals with SP (27 female and 11 male patients; median age at CRC diagnosis, 58.5 y) attending genetics clinics. Tumor samples were pathologically reviewed, screened for somatic BRAF and KRAS mutations, and analyzed immunohistochemically for mismatch repair protein (MMR) expression. Tumors were spread throughout the large intestine, with 64% located in the proximal colon. Mutations in BRAF and KRAS and immunohistochemical evidence of MMR deficiency were found in 46%, 5%, and 38%, respectively. Nearly half of CRCs were BRAF/KRAS wild type, and these were associated with distal location (63%) and MMR proficiency (84%). Overexpression of p53 and/or evidence of β-catenin activation were identified in 13 CRCs. Ten patients (26%) had synchronous or metachronous CRCs. In conclusion, the majority of CRCs arising in individuals with SP do not harbor molecular hallmarks of serrated pathway CRCs but show a diverse range of molecular profiles. The high proportion of multiple CRCs suggests that individuals with SP would benefit from frequent colonoscopic surveillance and from a consideration of a more extensive colectomy at the time of CRC diagnosis.

Serrated polyps of the large intestine: current understanding of diagnosis, pathogenesis, and clinical management

Approximately 30% of colorectal carcinomas develop via the serrated neoplasia pathway characterized by widespread DNA methylation and frequent BRAF mutation. Serrated polyps represent a heterogeneous group of polyps which are the precursor lesions to serrated pathway colorectal carcinomas. The histological classification of serrated polyps has evolved over the last two decades to distinguish three separate entities: hyperplastic polyp, sessile serrated adenoma (SSA), and traditional serrated adenoma (TSA). The malignant potential of SSAs and TSAs has been clearly demonstrated. SSAs are more challenging to detect by colonoscopy and are likely to account for some interval carcinomas of the proximal colon. Serrated polyposis syndrome is now widely recognized as conferring a high risk of colorectal carcinoma although its cause remains elusive. The current understanding of the actual malignant potential of each serrated polyp subtype is still limited due to the lack of large-scale prospective studies. Patient management guidelines have been recently updated although high-level evidence to support them is still required.

Proximal colon cancers and the serrated pathway: a systematic analysis of precursor histology and BRAF mutation status

Although the serrated neoplasia pathway is thought to give rise to the majority of sporadic microsatellite instability-high (MSI-H) colon cancer, the exact proportion of these tumors that arise from serrated precursors has not been fully studied. Tubular and tubulovillous adenomas with features of the serrated neoplasia pathway have been described, and unlike sessile serrated adenomas, these lesions lack BRAF mutations. The contribution of these adenomas to sporadic MSI-H colon cancer is unclear. To this end, we conducted an analysis of right-sided sporadic MSI-H and microsatellite stable (MSS) colon cancer, with emphasis on precursor lesions. Overall 25% (19/75) of MSI-H colon cancer had a precursor, of which only 4 were recognized histologically as arising from a sessile serrated adenoma, and the remaining were best classified as adenomas. Of the 31 (of 89) MSS colon cancers with a precursor, only 1 was a sessile serrated adenoma (P=0.06). Histological analysis of the precursor adenomas to sporadic MSI-H colon cancer demonstrated a high frequency of crypt serrations compared with MSS colon cancer (93 vs 36%, P<0.001). BRAF mutations were found in 57/75 (76%) sporadic MSI-H and 10/89 (11%) MSS colon cancers (P<0.001). Molecular analysis demonstrated BRAF mutations in 11/12 adenoma and 3/3 sessile serrated adenoma precursors adjacent to BRAF-mutated MSI-H colon cancer. Similarly, all 4 precursors to BRAF-mutated MSS colon cancer were also BRAF mutated. The presence of BRAF mutations in these adenomatous precursors suggests that they represent sessile serrated adenomas with complete cytologic dysplasia. Finally, patients with sporadic MSI-H colon cancer were more likely to harbour synchronous sessile serrated adenomas (20 vs 8%; P=0.023). This is the largest study to rigorously evaluate the precursor and synchronous lesions in patients with right-sided colon cancer. Detailed molecular and histological analysis of these lesions confirms the importance of serrated precursors in the development of sporadic MSI-H colon cancer.

Serrated lesions of the colorectum: review and recommendations from an expert panel

Serrated lesions of the colorectum are the precursors of perhaps one-third of colorectal cancers (CRCs). Cancers arising in serrated lesions are usually in the proximal colon, and account for a disproportionate fraction of cancer identified after colonoscopy. We sought to provide guidance for the clinical management of serrated colorectal lesions based on current evidence and expert opinion regarding definitions, classification, and significance of serrated lesions. A consensus conference was held over 2 days reviewing the topic of serrated lesions from the perspectives of histology, molecular biology, epidemiology, clinical aspects, and serrated polyposis. Serrated lesions should be classified pathologically according to the World Health Organization criteria as hyperplastic polyp, sessile serrated adenoma/polyp (SSA/P) with or without cytological dysplasia, or traditional serrated adenoma (TSA). SSA/P and TSA are premalignant lesions, but SSA/P is the principal serrated precursor of CRCs. Serrated lesions have a distinct endoscopic appearance, and several lines of evidence suggest that on average they are more difficult to detect than conventional adenomatous polyps. Effective colonoscopy requires an endoscopist trained in the endoscopic appearance of serrated lesions. We recommend that all serrated lesions proximal to the sigmoid colon and all serrated lesions in the rectosigmoid > 5 mm in size, be completely removed. Recommendations are made for post-polypectomy surveillance of serrated lesions and for surveillance of serrated polyposis patients and their relatives.

Outcomes of a 5-year follow-up of patients with sessile serrated adenomas

OBJECTIVE

Sessile serrated adenomas (SSAs) are precursors to colorectal cancer (CRC). The purpose of this study is to determine the occurrence of new polyps and CRC in patients with an SSA over a 5-year follow-up interval.

METHODS

This study is a retrospective chart review of patients with SSAs diagnosed at colonoscopy in 2005. Abstracted information included patient demographics, colonoscopy information, and polyp characteristics.

RESULTS

During 2005, 34 SSAs and 5 mixed SSAs were identified in 33 patients. The mean patient age was 66 years and 58% were female. There was a family history of CRC in 45%, prior polyps in 33%, and previous CRC in 15%. The mean SSA size was 11 mm. SSAs were located proximal to the splenic flexure in 70%. Low-grade dysplasia was present in 3% of SSAs and 80% mixed SSAs. Synchronous adenomatous and hyperplastic polyps occurred respectively in 45% and 21%. High-grade dysplasia was present in 12% of the adenomas. Twenty-two patients underwent subsequent colonoscopies with 20 new SSAs and 1 mixed SSA identified. In SSAs low-grade dysplasia occurred in 10% and high-grade dysplasia in 5%. Low-grade dysplasia was present in the mixed SSA. Synchronous adenomatous and hyperplastic polyps occurred respectively in 45% and 37%. High-grade dysplasia was present in 10% of adenomas and CRC occurred in 1 (5%) patient.

CONCLUSIONS

SSAs occurred more frequently in females and in the right colon. Dysplasia occurred in a small subset of SSAs. There was a high rate of prior and subsequent CRC in patients with SSAs.

Linkage to chromosome 2q32.2-q33.3 in familial serrated neoplasia (Jass syndrome)

Causative genetic variants have to date been identified for only a small proportion of familial colorectal cancer (CRC). While conditions such as Familial Adenomatous Polyposis and Lynch syndrome have well defined genetic causes, the search for variants underlying the remainder of familial CRC is plagued by genetic heterogeneity. The recent identification of families with a heritable predisposition to malignancies arising through the serrated pathway (familial serrated neoplasia or Jass syndrome) provides an opportunity to study a subset of familial CRC in which heterogeneity may be greatly reduced. A genome-wide linkage screen was performed on a large family displaying a dominantly-inherited predisposition to serrated neoplasia genotyped using the Affymetrix GeneChip Human Mapping 10 K SNP Array. Parametric and nonparametric analyses were performed and resulting regions of interest, as well as previously reported CRC susceptibility loci at 3q22, 7q31 and 9q22, were followed up by finemapping in 10 serrated neoplasia families. Genome-wide linkage analysis revealed regions of interest at 2p25.2-p25.1, 2q24.3-q37.1 and 8p21.2-q12.1. Finemapping linkage and haplotype analyses identified 2q32.2-q33.3 as the region most likely to harbour linkage, with heterogeneity logarithm of the odds (HLOD) 2.09 and nonparametric linkage (NPL) score 2.36 (P = 0.004). Five primary candidate genes (CFLAR, CASP10, CASP8, FZD7 and BMPR2) were sequenced and no segregating variants identified. There was no evidence of linkage to previously reported loci on chromosomes 3, 7 and 9.

Individuals with sessile serrated polyps express an aggressive colorectal phenotype

BACKGROUND

Sessile serrated polyps are precursors of colorectal cancer arising from molecular pathways distinct from conventional adenomas. The association between sessile serrated polyps and conventional adenomas is not well known.

OBJECTIVE

We hypothesize that individuals who have coexistent sessile serrated polyps and conventional adenomas express a more severe phenotype than those harboring lesions from only one pathway. We compare colorectal phenotypes among individuals with sessile serrated polyps, those with conventional adenomas, and those expressing both.

DESIGN

This investigation is a retrospective cross-sectional study of 3 cohorts.

SETTINGS

This study was conducted in multiple centers within 1 health care system.

PATIENTS

Individuals with sessile serrated polyps and/or conventional adenomas on first lifetime colonoscopy were included in the study.

MAIN OUTCOME MEASURES

The demographics and polyp characteristics were compared among 3 cohorts to determine the differences in phenotypic expression.

RESULTS

Two hundred sixty individuals with sessile serrated polyps and 173 with only conventional adenomas were included. The disease phenotype was most severe in individuals with coexistent sessile serrated polyps and adenomas. The sessile serrated polyps in this cohort were larger (P = .01) than in the serrated-only cohort. The conventional adenomas in this cohort were more numerous (P = .035) and more advanced (P = .046) than in the adenoma-only cohort. Synchronous colorectal cancers were found exclusively in the cohorts with sessile serrated polyps, although this did not reach statistical significance (P = .06).

LIMITATIONS

Cross-sectional design precluded the ability to assess for metachronous lesions. Sessile serrated polyps, but not all polyps, were reviewed.

CONCLUSIONS

Individuals who coexpress sessile serrated polyps and conventional adenomas have an aggressive colorectal phenotype. They harbor larger sessile serrated polyps and more numerous and advanced adenomas than individuals with only sessile serrated polyps or adenomas. Synchronous colorectal cancers were found exclusively in cohorts with sessile serrated polyps. Individuals with sessile serrated polyps, especially with coexistent conventional adenomas, appear to be a high-risk group, which needs to be accounted for when calculating postpolypectomy surveillance intervals.

Serrated polyposis: an enigmatic model of colorectal cancer predisposition

Serrated polyposis has only recently been accepted as a condition which carries an increased personal and familial risk of colorectal cancer. Described over four decades ago, it remains one of the most underrecognized and poorly understood of all the intestinal polyposes. With a variety of phenotypic presentations, it is likely that serrated polyposis represents a group of diseases rather than a single entity. Further, neoplastic progression in serrated polyposis may be associated with premature aging in the normal mucosa, typified by widespread gene promoter hypermethylation. From this epigenetically altered field, arise diverse polyps and cancers which show a range of molecular features. Despite a high serrated polyp count, only one-third of colorectal cancers demonstrate a BRAF V600E mutation, the molecular hallmark of the canonical serrated pathway, suggesting that though multiple serrated polyps act as a marker of an abnormal mucosa, the majority of CRC in these patients arise within lesions other than BRAF-mutated serrated polyps.

The clinical significance of serrated polyps

Colorectal cancer (CRC) is a heterogeneous disorder than arises via multiple distinct pathways, such as the serrated pathway, in which serrated polyps (including variants of hyperplastic polyps) are the precursor lesions. Approximately 15-20% of all CRCs arise via the serrated pathway, and these serrated carcinomas are clinically, morphologically, and molecularly distinct from conventional CRCs. The prevention of serrated carcinomas represents an important clinical challenge. Gastroenterologists need to recognize and remove potential precursor lesions and implement a post-polypectomy surveillance program when appropriate. This article focuses on the characteristics and significance of clinically relevant serrated polyps and addresses implications for CRC prevention practices.

Comprehensive evaluation of colorectal polyps in specimens from endoscopic biopsies

Modern evaluation of specimens from biopsies of colorectal polyps has become increasingly complex because of tremendous progress in the understanding of colorectal neoplasia. Although pathologists are generally familiar with the basic handling of carcinoma in the setting of polypectomies or resections, the comprehensive evaluation of specimens from biopsies of colorectal polyps obtained with forceps is far from intuitive and has yet to be reviewed. Comprehensive evaluation requires always addressing several key issues, even when dealing with seemingly routine cases. These issues include taking further action when initial sections lack polyps, accurately quantitating polyps, accurately classifying polyps, determining whether thresholds are met for considering conditions at high risk for carcinoma, detecting incidental findings other than polyps, and determining which incidental findings are clinically significant. In particular, polyposis with attenuated phenotype or Lynch syndrome may be clinically occult, and the possibility of these entities should always be kept in mind, regardless of age or history. Ancillary studies performed immediately on carcinoma that is detected at biopsy guides surgery, guides medical therapy, prognosticates, provides evidence for hereditary neoplasia, and guides surveillant colonoscopy for the family.

Risk factors for colorectal cancer in patients with multiple serrated polyps: a cross-sectional case series from genetics clinics

Background

Patients with multiple serrated polyps are at an increased risk for developing colorectal cancer (CRC). Recent reports have linked cigarette smoking with the subset of CRC that develops from serrated polyps. The aim of this work therefore was to investigate the association between smoking and the risk of CRC in high-risk genetics clinic patients presenting with multiple serrated polyps.

Methods and Findings

We identified 151 Caucasian individuals with multiple serrated polyps including at least 5 outside the rectum, and classified patients into non-smokers, current or former smokers at the time of initial diagnosis of polyposis. Cases were individuals with multiple serrated polyps who presented with CRC. Controls were individuals with multiple serrated polyps and no CRC. Multivariate logistic regression was performed to estimate associations between smoking and CRC with adjustment for age at first presentation, sex and co-existing traditional adenomas, a feature that has been consistently linked with CRC risk in patients with multiple serrated polyps. CRC was present in 56 (37%) individuals at presentation. Patients with at least one adenoma were 4 times more likely to present with CRC compared with patients without adenomas (OR = 4.09; 95%CI 1.27 to 13.14; P = 0.02). For females, the odds of CRC decreased by 90% in current smokers as compared to never smokers (OR = 0.10; 95%CI 0.02 to 0.47; P = 0.004) after adjusting for age and adenomas. For males, there was no relationship between current smoking and CRC. There was no statistical evidence of an association between former smoking and CRC for both sexes.

Conclusion

A decreased odds for CRC was identified in females with multiple serrated polyps who currently smoke, independent of age and the presence of a traditional adenoma. Investigations into the biological basis for these observations could lead to non-smoking-related therapies being developed to decrease the risk of CRC and colectomy in these patients.