Molecular classification and genetic pathways in hyperplastic polyposis syndrome

Risk of Colorectal Cancer in Serrated Polyposis Syndrome: A Systematic Review and Meta-analysis

BACKGROUND & AIMS

Serrated polyposis syndrome (SPS) is characterized by development of numerous serrated lesions throughout the colorectum and increased risk of colorectal cancer (CRC). However, SPS has been an underrecognized CRC predisposition syndrome, and the true risk of CRC in SPS, both overall and in surveillance, is not known. The aim of this systematic review and meta-analysis is to describe the risk of CRC in patients with SPS.

METHODS

Electronic databases were searched on March 25, 2021, for studies describing CRC risk in SPS. Random-effects meta-analysis was performed to assess pooled risk of CRC among SPS patients. Primary outcomes were risk of CRC at time of SPS diagnosis and during surveillance following diagnosis of SPS. Secondary outcomes included risk of CRC prior to diagnosis of SPS and effect of World Health Organization subtype on CRC risk.

RESULTS

Thirty-six studies including 2788 patients with SPS were included in the analysis. Overall risk of CRC in SPS was 19.9% (95% confidence interval [CI], 15.3%-24.5%). CRC risk at the time of diagnosis was 14.7% (95% CI, 11.4%-18.8%), while risk during surveillance was 2.8% (95% CI, 1.8%-4.4%), or 7 cases per 1000 person-years. SPS patients also had a high incidence of history of CRC prior to SPS diagnosis (7.0%; 95% CI, 4.6%-11.7). Subgroup analysis did not reveal any significant differences based on World Health Organization subtype.

CONCLUSIONS

Our meta-analysis demonstrated that patients with SPS have an elevated risk of CRC, which is highest at the time of diagnosis and suggests the importance of early SPS recognition and screening to modify CRC risk. The persistently elevated CRC risk during surveillance supports current guidelines recommending heightened surveillance protocols.

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).

Management of Serrated Polyps of the Colon

PURPOSE OF REVIEW

The purpose of this review is to summarize the management of serrated colorectal polyps (SPs), with a particular focus on the most common premalignant SP, sessile serrated adenoma or polyp (SSA/P). These lesions present a challenge for endoscopists with respect to detection and resection, and are also susceptible to pathologic misdiagnosis.

RECENT FINDINGS

Patients with SSA/Ps are at an increased risk of future colorectal neoplasia, including advanced polyps and cancer. Reasonable benchmarks for SP detection rates are 5-7% for SSA/Ps and 10-12% for proximal SPs. Certain endoscopic techniques such as chromoendoscopy, narrow band imaging, water immersion, and wide-angle viewing may improve SSA/P detection. Emerging endoscopic techniques such as underwater polypectomy, suction pseudopolyp technique, and piecemeal cold snare polypectomy are helpful tools for the endoscopist's armamentarium for removing SSA/Ps. Proper orientation of SSA/P specimens can improve the accuracy of pathology readings. Patients with confirmed SSA/Ps and proximal HPs should undergo surveillance at intervals similar to what is recommended for patients with conventional adenomas. Patients with SSA/Ps may also be able to lower their risk of future polyps by targeting modifiable risk factors including tobacco and alcohol use and high-fat diets. NSAIDs and aspirin appear to be protective agents. SPs and SSA/Ps in particular are important colorectal cancer precursors that merit special attention to ensure adequate detection, resection, and surveillance.

MUTYH-associated colon disease: Adenomatous polyposis is only one of the possible phenotypes. A family report and literature review

Aims and background

The MutY human homologue gene (MUTYH) is responsible for about a quarter of attenuated familial adenomatous polyposis. Occasionally, it has been associated with hyperplastic polyps and serrated adenoma. We report a family where the same MUTYH mutation determined four different phenotypes, including a case of hyperplastic polyposis syndrome.

Patients and methods

A family with a history of right-sided colon cancer and multiple colonic polyposis was investigated. Genetic tests were correlated with clinical findings to define phenotypic manifestations of MUTYH mutations. The pertinent English-language literature was reviewed to evaluate the risk of malignancy of MUTYH and the role of prophylactic surgery.

Results

Three male siblings carried a biallelic MUTYH mutation (G382D-exon13), while the fourth was heterozygote. One developed an isolated cecal cancer at the age of 48. Another, aged 38, was diagnosed with numerous minute colonic and rectal polyps and underwent a proctocolectomy, with final pathology showing a picture of hyperplastic and lymphoid polyposis. The third biallelic brother, 46 years old, developed four hyperplastic lesions, while the heterozygote brother had a large flat serrated adenoma of the right colon removed at the age of 50.

Conclusion

Many aspects of MUTYH mutation still need to be clarified and one of them regards the different phenotypic expressions. Although the majority of reported cases manifested attenuated adenomatous polyposis, hyperplastic polyps and serrated adenomas appear to be more common than expected. Presenting hyperplastic polyposis syndrome is very unusual and may represent a clinical dilemma for correct management. Current evidence suggests to handle MUTYH-associated polyposis as typical FAP.

Serrated lesions and serrated polyposis syndrome

The serrated pathway has been shown to be an alternative colorectal carcinogenetic route potentially accounting for up to one third of all CRCs. Serrated lesions, particularly SSPs, have been a focus of research during the past few years. They have well-established histological and molecular characteristics that account for their potential carcinogenetic risk through the accumulation BRAF, KRAS and methylator profile (CpG) mutations. Their endoscopic identification and resection represent a challenge because of their specific characteristics, and the need for an adequate specimen for histological diagnosis. Knowledge of these lesions is key, as is the adoption of established criteria for their endoscopic description and histological diagnosis. SPS is the maximum expression of involvement by serrated lesions, is associated with increased risk for CRC, and requires attentive endoscopic follow-up, as well as family screening. While the exact etiopathogenic mechanism remains unknown, current research will likely provide us with appropriate answers in the not too distant future.

Gastrointestinal tract cancers: Genetics, heritability and germ line mutations

Gastrointestinal (GI) tract cancers that arise due to genetic mutations affect a large number of individuals worldwide. Even though many of the GI tract cancers arise sporadically, few of these GI tract cancers harboring a hereditary predisposition are now recognized and well characterized. These include Cowden syndrome, MUTYH-associated polyposis, hereditary pancreatic cancer, Lynch syndrome, Peutz-Jeghers syndrome, familial adenomatous polyposis (FAP), attenuated FAP, serrated polyposis syndrome, and hereditary gastric cancer. Molecular characterization of the genes that are involved in these syndromes was useful in the development of genetic testing for diagnosis and also facilitated understanding of the genetic basis of GI cancers. Current knowledge on the genetics of GI cancers with emphasis on heritability and germ line mutations forms the basis of the present review.

Serrated Polyps and Serrated Polyposis Syndrome

Colorectal serrated polyps are intermediate lesions in the serrated neoplastic pathway, which account for up to 30% of colorectal cancers. This pathway is biologically distinct from the adenoma-to-carcinoma sequence, with associated cancers exhibiting mutations in the BRAF oncogene, DNA promoter hypermethylation, and microsatellite instability. An evolving understanding of these unique lesions has led to the development of a more accurate classification, improved endoscopic identification, and tailored clinical management guidelines. This article reviews serrated polyps and serrated polyposis syndrome.

Colorectal cancer risk factors in patients with serrated polyposis syndrome: a large multicentre study

OBJECTIVE

Serrated polyposis syndrome (SPS) is associated with an increased colorectal cancer (CRC) risk, although the magnitude of the risk remains uncertain. Whereas intensive endoscopic surveillance for CRC prevention is advised, predictors that identify patients who have high CRC risk remain unknown. We performed a multicentre nationwide study aimed at describing the CRC risk in patients with SPS and identifying clinicopathological predictors independently associated with CRC.

DESIGN

From March 2013 through September 2014, patients with SPS were retrospectively recruited at 18 Spanish centres. Data were collected from medical, endoscopy and histopathology reports. Multivariate logistic regression was performed to identify CRC risk factors.

RESULTS

In 296 patients with SPS with a median follow-up time of 45 months (IQR 26-79.7), a median of 26 (IQR 18.2-40.7) serrated polyps and 3 (IQR 1-6) adenomas per patient were detected. Forty-seven patients (15.8%) developed CRC at a mean age of 53.9±12.8, and 4 out of 47 (8.5%) tumours were detected during surveillance (cumulative CRC incidence 1.9%). Patients with >2 sessile serrated adenomas/polyps (SSA/Ps) proximal to splenic flexure and ≥1 proximal SSA/P with high-grade dysplasia were independent CRC risk factors (incremental OR=2, 95% CI 1.22 to 3.24, p=0.006). Patients with no risk factors showed a 55% decrease in CRC risk (OR=0.45, 95% CI 0.24 to 0.86, p=0.01).

CONCLUSIONS

Patients with SPS have an increased risk of CRC, although lower than previously published. Close colonoscopy surveillance in experienced centres show a low risk of developing CRC (1.9% in 5 years). Specific polyp features (SSA/P histology, proximal location and presence of high-grade dysplasia) should be used to guide clinical management.

Clinical manifestations of colorectal cancer patients from a large multicenter study in Colombia

Colorectal cancer (CRC) is a major public health problem, and its incidence is rising in developing countries. However, studies characterizing CRC clinicopathological features in cases from developing countries are still lacking. The goal of this study was to evaluate clinicopathological and demographic features in one of the largest CRC studies in Latin America.The study involved over 1525 CRC cases recruited in a multicenter study in Colombia between 2005 and 2014 as part of ongoing genetic and epidemiological studies. We gathered clinicopathological data such as age at diagnosis, sex, body mass index, tobacco and alcohol consumption, family history of cancer, and tumor features including location, histological type, and stage. Statistical analyses were performed to test the association between age of onset, sex, and clinical manifestations.The average age at CRC diagnosis was 57.4 years, with 26.5% of cases having early-onset CRC (diagnosed by age 50 years). Most cases were women (53.2%; P = 0.009), 49.2% were overweight or obese, 49.1% were regular alcohol drinkers, 52% were smokers/former smokers, and 12.2% reported relatives with cancer. Most tumors in the study were located in the rectum (42.7%), were adenocarcinomas (91.5%), and had advanced stage (T3-T4, 79.8%). Comparisons by sex found that male cases were more likely to be obese (36.5% vs 31.1%; P = 0.001), less likely to have a family history of cancer (9.7% vs 15.3%; P = 0.016), and more likely to have advanced-stage tumors (83.9% vs 76.1%; P = 0.036). Comparisons by age of onset found that early-onset cases were more likely to be women (59.3% vs 51.0%; P = 0.005) and report a family history of cancer (17.4% vs 10.2%; P = 0.001).To our knowledge, our study is the largest report of clinicopathological characterization of Hispanic CRC cases, and we suggest that further studies are needed to understand CRC etiology in diverse Hispanic populations.

Serrated polyposis associated with a family history of colorectal cancer and/or polyps: The preferential location of polyps in the colon and rectum defines two molecular entities

Serrated polyposis (SPP) is characterized by the development of multiple serrated polyps and an increased predisposition to colorectal cancer (CRC). In the present study, we aimed to characterize, at a clinical and molecular level, a cohort of SPP patients with or without a family history of SPP and/or polyps/CRC (SPP-FHP/CRC). Sixty-two lesions from 12 patients with SPP-FHP/CRC and 6 patients with sporadic SPP were included. The patients with SPP-FHP/CRC presented with an older mean age at diagnosis (p=0.027) and a more heterogeneous histological pattern of lesions (p=0.032) than the patients with sporadic SPP. We identified two molecular forms of SPP-FHP/CRC, according to the preferential location of the lesions: proximal/whole-colon or distal colon. Mismatch repair (MMR) gene methylation [mutS homolog 6 (MSH6)/mutS homolog 3 (MSH3)] or loss of heterozygosity (LOH) of D2S123 (flanking MSH6) were detected exclusively in the former (p=3.0×10⁻⁷), in most early lesions. Proximal/whole-colon SPP-FHP/CRC presented a higher frequency of O-6-methylguanine-DNA methyltransferase (MGMT) methylation/LOH, microsatel-lite instability (MSI) and Wnt mutations (19/29 vs. 7/17; 16/23 vs. 1/14, p=2.2×10⁻⁴; 15/26 vs. 2/15, p=0.006; 14/26 vs. 4/20, p=0.02) but a lower frequency of B-raf proto-oncogene, serine/threonine kinase (BRAF) mutations (7/30 vs. 12/20, p=0.0089) than the distal form. CRC was more frequent in cases of Kirsten rat sarcoma viral oncogene homolog (KRAS)-associated proximal/whole-colon SPP-FHP/CRC than in the remaining cases (4/4 vs. 1/8, p=0.01). Thus, SPP-FHP/CRC appears to be a specific entity, presenting two forms, proximal/whole-colon and distal, which differ in the underlying tumor initiation pathways. Early MGMT and MMR gene deficiency in the former may underlie an inherited susceptibility to genotoxic stress.

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.

Type 1 serrated polyposis represents a predominantly female disease with a high prevalence of dysplastic serrated adenomas, without germline mutation in MUTYH, APC, and PTEN genes

AIM

The aim of this article is to clarify the epidemiologic, clinical, endoscopic, biological and genetic characteristics of type 1 serrated polyposis patients.

PATIENTS AND METHODS

Consecutive patients responding to the WHO definition of type 1 serrated polyposis in one reference center for polyposis patients accepted genetic counseling. Detailed data on previous endoscopies, histology, and life habits were recorded, after informed consent, germline analysis of MUTYH, APC, and PTEN germline mutations. Molecular biology was tested on available fixed tissue from different lesion types.

RESULTS

We included 29 patients (mean age 53.5 years, 21 women (72.4%)), four with a personal history of colorectal cancer (CRC), with a mean of 11.6 SSAs, with associated hyperplastic polyps in 93.1% and adenomas in 82.8%. SSAs showed no dysplasia in 46.9% of lesions (three of 29 patients), LGD in 51.9% (22/29 patients), and HGD in 1.2% (four of 29 patients). Dysplasia was more frequent in proximal SSAs and in women. Colectomy 15 patients (51.7%), upper digestive neoplasms: eight patients (27.5%); smokers: 24 patients (82.8%); family history of CRC: 16 patients (55.2%). Biology: MSI-H phenotype in one SSA, V600E BRAF mutation in 95% of SSAs; MGMT hypermethylation in three of 17 SSAs. No germline mutation was detected in MYH, APC or PTEN genes.

CONCLUSION

Type 1 serrated polyposis corresponds to a majority of women, with a high prevalence of smokers, a high prevalence of dysplastic serrated adenomas, particularly in females, without identified germline mutation in targeted predisposing genes.

Inherited predisposition to colorectal cancer: towards a more complete picture

Colorectal carcinoma (CRC) is the third most common cancer worldwide. Hereditary factors are important in 15%-35% of affected patients. This review provides an update on the genetic basis of inherited predisposition to CRC. Currently known genetic factors include a group of highly penetrant mutant genes associated with rare mendelian cancer syndromes and a group of common low-penetrance alleles that have been identified through genetic association studies. Additional mechanisms, which may underlie a predisposition to CRC, will be outlined, for example, variants in intermediate penetrance alleles. Recent findings, including mutations in POLE, POLD1 and NTHL1, will be highlighted, and we identify gaps in present knowledge and consider how these may be addressed through current and emerging genomic approaches. It is expected that identification of the missing heritable component of CRC will be resolved through evermore comprehensive cataloguing and phenotypic annotation of CRC-associated variants identified through sequencing approaches. This will have important clinical implications, particularly in areas such as risk stratification, public health and CRC prevention.

Management of Patients with Hereditary Colorectal Cancer Syndromes

Colorectal cancer (CRC) is one of the most important causes of death in the world. Hereditary CRC is found in 5–10% of CRC patients. In this review, we will focus on the major forms of hereditary CRC and their management according to the most recent literature available.

Serrated neoplasia-role in colorectal carcinogenesis and clinical implications

Colorectal cancer (CRC) is considered a heterogeneous disease, both regarding pathogenesis and clinical behaviour. Four decades ago, the adenoma-carcinoma pathway was presented as the main pathway towards CRC, a conclusion that was largely based on evidence from observational morphological studies. This concept was later substantiated at the genomic level. Over the past decade, evidence has been generated for alternative routes in which CRC might develop, in particular the serrated neoplasia pathway. Providing indisputable evidence for the neoplastic potential of serrated polyps has been difficult. Reasons include the absence of reliable longitudinal observations on individual serrated lesions that progress to cancer, a shortage of available animal models for serrated lesions and challenging culture conditions when generating organoids of serrated lesions for in vitro studies. However, a growing body of circumstantial evidence has been accumulated, which indicates that ≥15% of CRCs might arise through the serrated neoplasia pathway. An even larger amount of post-colonoscopy colorectal carcinomas (carcinomas occurring within the surveillance interval after a complete colonoscopy) have been suggested to originate from serrated polyps. The aim of this Review is to assess the current status of the serrated neoplasia pathway in CRC and highlight clinical implications.

Clinicopathological Characteristics of Serrated Polyposis Syndrome in Korea: Single Center Experience

Background/Aim. Serrated polyposis syndrome (SPS) is a rare condition characterized by multiple serrated polyps throughout the colon and rectum. The aim of this study was to evaluate the clinicopathological characteristics of SPS in Koreans. Methods. This retrospective analysis of prospectively collected data was performed using information from the endoscopy, clinical records, and pathology database system of Uijeongbu St. Mary's Hospital. Consecutive patients satisfying the updated 2010 World Health Organization criteria for SPS between June 2011 and May 2014 were enrolled. Results. Of the 17,552 patients who underwent colonoscopies during the study period, 11 (0.06%) met the criteria for SPS. The mean age of these patients was 55.6 years. Ten patients (91%) were males. None had a family history of CRC or a first-degree relative with SPS. Seven patients (64%) had synchronous advanced adenoma. One patient had coexistence of SPS with CRC that was diagnosed at the initial colonoscopy. Five patients (45%) had more than 30 serrated polyps. One of the patients underwent surgery and 10 underwent endoscopic resection. Conclusion. The prevalence of SPS in this study cohort was comparable to that in Western populations. Considering the high risk of CRC, correct diagnosis and careful follow-up for SPS are necessary.

Genetic predisposition to colorectal cancer: Where we stand and future perspectives

The development of colorectal cancer (CRC) can be influenced by genetic factors in both familial cases and sporadic cases. Familial CRC has been associated with genetic changes in high-, moderate- and low-penetrance susceptibility genes. However, despite the availability of current gene-identification techniques, the genetic causes of a considerable proportion of hereditary cases remain unknown. Genome-wide association studies of CRC have identified a number of common low-penetrance alleles associated with a slightly increased or decreased risk of CRC. The accumulation of low-risk variants may partly explain the familial risk of CRC, and some of these variants may modify the risk of cancer in patients with mutations in high-penetrance genes. Understanding the predisposition to develop CRC will require investigators to address the following challenges: the identification of genes that cause uncharacterized hereditary cases of CRC such as familial CRC type X and serrated polyposis; the classification of variants of unknown significance in known CRC-predisposing genes; and the identification of additional cancer risk modifiers that can be used to perform risk assessments for individual mutation carriers. We performed a comprehensive review of the genetically characterized and uncharacterized hereditary CRC syndromes and of low- and moderate-penetrance loci and variants identified through genome-wide association studies and candidate-gene approaches. Current challenges and future perspectives in the field of CRC predisposition are also discussed.

Serrated polyposis syndrome

SUMMARY 

Serrated polyposis syndrome, also called hyperplastic polyposis, is a condition characterized by numerous neoplastic polyps throughout the colon and rectum. The polyps possess a distinct serrated morphology. The term serrated refers to the ‘saw-tooth’ pattern formed by epithelial cells in the colonic crypts on standard histologic preparations. Historically, serrated lesions have been lumped together under the term ‘hyperplastic polyps’, and were assumed to carry no malignant potential. Over the past decade, however, an increasing body of evidence suggests that serrated lesions exist along a spectrum and represent an alternative molecular pathway to the development of colorectal cancer in contrast to the traditional adenocarcinoma sequence. Although a hallmark genetic signature for serrated polyposis syndrome remains unidentified, this is an area of active investigation.

Incidence of colonic neoplasia in patients with serrated polyposis syndrome who undergo annual endoscopic surveillance

BACKGROUND & AIMS

Patients with serrated polyposis syndrome (SPS) are advised to undergo endoscopic surveillance for early detection of polyps and prevention of colorectal cancer (CRC). The optimal surveillance and treatment regimen is unknown. We performed a prospective study to evaluate a standardized endoscopic treatment protocol in a large cohort of patients with SPS.

METHODS

We followed a cohort of patients with SPS who received annual endoscopic surveillance at the Academic Medical Centre in Amsterdam, The Netherlands from January 2007 through December 2012. All patients underwent clearing colonoscopy with removal of all polyps ≥3 mm. After clearance, subsequent follow-up colonoscopies were scheduled annually. The primary outcomes measure was the incidence of CRC and polyps. Secondary outcomes were the incidence of complications and the rate of preventive surgery.

RESULTS

Successful endoscopic clearance of all polyps ≥3 mm was achieved in 41 of 50 (82%) patients. During subsequent annual surveillance, with a median follow-up time of 3.1 years (interquartile range, 1.5-4.3 years), CRC was not detected. The cumulative risks of detecting CRC, advanced adenomas, or large (≥10 mm) serrated polyps after 3 surveillance colonoscopies were 0%, 9%, 34%, respectively. Twelve patients (24%) were referred for preventive surgery; 9 at initial colonoscopy and 3 during surveillance. Perforations or severe bleeding did not occur.

CONCLUSIONS

Annual surveillance with complete removal of all polyps ≥3 mm with timely referral of selected high-risk patients for prophylactic surgery prevents development of CRC in SPS patients without significant morbidity. Considering the substantial risk of polyp recurrence, close endoscopic surveillance in SPS seems warranted. www.trialregister.nl ID NTR2757.

Germline Mutations in the Polyposis-Associated Genes BMPR1A, SMAD4, PTEN, MUTYH and GREM1 Are Not Common in Individuals with Serrated Polyposis Syndrome

Background

Recent reports have observed that individuals with serrated polyps, some of whom meet the clinical diagnostic criteria for Serrated Polyposis Syndrome (SPS), are among those who carry germline mutations in genes associated with polyposis syndromes including; (1) genes known to underlie hamartomatous polyposes (SMAD4, BMPR1A, and PTEN), (2) MUTYH-associated polyposis and (3) GREM1 in Hereditary Mixed Polyposis Syndrome (HMPS). The aim of this study was to characterise individuals fulfilling the current WHO criteria for SPS for germline mutations in these polyposis-associated genes.

Methods

A total of 65 individuals with SPS (fulfilling WHO criteria 1 or 3), were recruited to the Genetics of Serrated Neoplasia study between 2000 and 2012, through multiple Genetics or Family Cancer Clinics within Australia, or from the New Zealand Familial Gastrointestinal Cancer Service. Individuals with SPS were tested for coding mutations and large deletions in the PTEN, SMAD4, and BMPR1A genes, for the MUTYH variants in exons 7 (Y179C) and 13 (G396D), and for the duplication upstream of GREM1.

Results

We found no variants that were likely to be deleterious germline mutations in the SPS cases in the PTEN, SMAD4, and BMPR1A genes. A novel variant in intron 2 (c.164+223T>C) of PTEN was identified in one individual and was predicted by in silico analysis to have no functional consequences. One further individual with SPS was found to be mono-allelic for the MUTYH G396D mutation. No individuals carried the recently reported duplication within GREM1.

Conclusions

Genes involved in the gastrointestinal hamartomatous polyposis, Hereditary Mixed Polyposis Syndrome and MUTYH-associated polyposis syndromes are not commonly altered in individuals with SPS.

Clinical subtypes and molecular characteristics of serrated polyposis syndrome

BACKGROUND & AIMS

We investigated clinical and molecular differences between the different phenotypes of serrated polyposis syndrome (SPS) and the frequency of mutations in BRAF or KRAS in polyps from patients with SPS.

METHODS

We collected data on clinical and demographic characteristics of 50 patients who fulfilled the criteria for SPS. Polymerase chain reaction and sequence analysis were used to identify BRAF and KRAS mutations in 432 polyps collected from 37 patients; we analyzed CpG island methylator phenotypes in 272 of these polyps.

RESULTS

Fifteen patients (30%) had type 1 SPS and 35 had type 2 SPS. There were no significant differences in age at diagnosis, sex, smoking frequency, body mass index, or colorectal cancer predisposition between groups of patients, or in the pathologic or molecular characteristics of their polyps. A familial history of colorectal cancer or colonic polyps was reported more frequently by patients with type 2 SPS. BRAF mutations were found in 63% of polyps and KRAS mutations were found in 9.9%; 43.4% of polyps had the CpG island methylator phenotype-high phenotype. A per-patient analysis revealed that all patients had a BRAF or KRAS mutation in more than 25% of their polyps; 84.8% of patients had a mutation in BRAF or KRAS in more than 50% of their polyps.

CONCLUSIONS

Except for a greater likelihood of familial history of colorectal cancer or colonic polyps in patients with type 2 SPS, we found no significant demographic, pathologic, or molecular differences between types 1 and 2 SPS. All patients had a BRAF or KRAS mutation in at least 25% of their polyps.

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.

Advanced precancerous lesions (APL) in the colonic mucosa

Colorectal cancer is a leading cause of cancer death worldwide. Most colorectal cancers are preventable. Surveillance colonoscopy is used to detect and remove precancerous lesions. Although the majority of precancerous lesions develop sporadically, some have an inherited component. In this review, we summarize the clinical, pathologic, and molecular features of advanced precancerous lesions of the colon. The most common and clinically important intestinal polyposis syndromes, and their genetics, are also discussed. Finally, current recommendations regarding the treatment and surveillance of precancerous lesions, both in the sporadic and in inherited setting, are reviewed.

Serrated polyposis is an underdiagnosed and unclear syndrome: the surgical pathologist has a role in improving detection

Serrated polyposis syndrome (SPS) is poorly defined and patients have an increased but unspecified risk for colorectal carcinoma through the serrated pathway. Despite this association SPS remains relatively obscure and is therefore likely underrecognized. We determined the frequency of SPS among patients with any serrated polyps (SPs) over a 6-month "index" period, and in doing so we assessed the ability of surgical pathologists to improve SPS detection. Particular attention was given to the index procedure to assess the potential predictive value of the findings resulting from a single colonoscopy. A total of 929 patients with at least 1 SP were identified, 17 of whom (1.8%) were determined to meet World Health Organization criteria for SPS. Nine patients met the first criterion (≥ 5 proximal SPs, 2 of which are > 10 mm); 4 met the third criterion (> 20 SPs of any size distributed throughout the colon); and 4 met both criteria. Although no specific SP size or number at the index procedure was clearly superior in its ability to predict SPS, > 50% of cases would be detected if a cutoff of ≥ 3 SPs or a single SP ≥ 15 mm at the index procedure is used. In summary, SPS is rare but more likely underdiagnosed. Additional studies to address the underlying genetic basis for SPS are ongoing in order to shed further light on this syndrome. Surgical pathologists are in a unique position to assist in this endeavor by identifying those patients who either meet or seem to be at high risk of meeting World Health Organization criteria.

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.

Phenotype and polyp landscape in serrated polyposis syndrome: a series of 100 patients from genetics clinics

Serrated polyposis syndrome (SPS), also known as hyperplastic polyposis, is a syndrome of unknown genetic basis defined by the occurrence of multiple serrated polyps in the large intestine and associated with an increased risk of colorectal cancer (CRC). There are a variety of SPS presentations, which may encompass a continuum of phenotypes modified by environmental and genetic factors. To explore the phenotype of SPS, we recorded the histologic and molecular characteristics of multiple colorectal polyps in patients with SPS recruited between 2000 and 2010 from genetics clinics in Australia, New Zealand, Canada, and the United States. Three specialist gastrointestinal pathologists reviewed the polyps, which they classified into conventional adenomas or serrated polyps, with various subtypes, according to the current World Health Organization criteria. Mutations in BRAF and KRAS and mismatch repair protein expression were determined in a subset of polyps. A total of 100 patients were selected for the study, of whom 58 were female and 42 were male. The total polyp count per patient ranged from 6 to 150 (median 30). The vast majority of patients (89%) had polyposis affecting the entire large intestine. From this cohort, 406 polyps were reviewed. Most of the polyps (83%) were serrated polyps: microvesicular hyperplastic polyps (HP) (n=156), goblet cell HP (n=25), sessile serrated adenoma/polyps (SSA/P) (n=110), SSA/P with cytologic dysplasia (n=28), and traditional serrated adenomas (n=18). A further 69 polyps were conventional adenomas. BRAF mutation was mainly detected in SSA/P with dysplasia (95%), SSA/P (85%), microvesicular HP (76%), and traditional serrated adenoma (54%), whereas KRAS mutation was present mainly in goblet cell HP (50%) and in tubulovillous adenoma (45%). Four of 6 SSA/Ps with high-grade dysplasia showed loss of MLH1/PMS2 expression. CRC was diagnosed in 39 patients who were more often found to have a conventional adenoma compared with patients without CRC (P=0.003). Patients with SPS referred to genetics clinics had a pancolonic disease with a high polyp burden and a high rate of BRAF mutation. The occurrence of CRC was associated with the presence of conventional adenoma.

Failure to recognize serrated polyposis syndrome in a cohort with large sessile colorectal polyps

BACKGROUND

Serrated polyposis syndrome (SPS) is a rare condition of multiple serrated colorectal polyps and cancers. Colorectal cancer risk is increased in SPS.

OBJECTIVE

We determined the prevalence of SPS in a cohort of patients with large (≥ 2 cm) sessile colorectal polyps and the rate at which the diagnosis was made by the clinicians.

DESIGN

Review of patient care database. The 2010 World Health Organization (WHO) criteria were used to identify cases of SPS.

SETTING

Tertiary academic center.

PATIENTS

529 consecutive patients referred for endoscopic resection of a sessile colorectal polyp ≥ 2 cm.

MAIN OUTCOME MEASUREMENTS

Prevalence of SPS in the cohort and frequency with which the referring physician and the endoscopist recognized SPS.

RESULTS

Of the 529 patients, 20 (4%) met the WHO criteria for SPS. Only 1 of these cases was suspected by a referring physician. Twelve cases (60%) were either diagnosed or suspected by the endoscopist at our center. Compared with all other patients without SPS, those with SPS were more likely to have an index lesion (the lesion that led to referral) that was serrated (60% vs 3.8%), to have a cecal or ascending colon index lesion (70% vs 45%), and to be current smokers (42% vs 15%). Including the first colonoscopy to remove the index lesion and 26 follow-up colonoscopies, the endoscopist at our center removed 183 serrated polyps from the 20 patients with SPS; of those polyps, 68 were >1 cm. Three patients were referred for surgical resection of involved colon. Eighteen of the 20 patients with SPS met the WHO criterion of 5 serrated polyps proximal to the sigmoid, of which 2 are >1 cm. Failure to recognize SPS by the referring physician was at least partly related to unrecognized serrated lesions. Failure to recognize SPS by the endoscopist at our institution was the result of not systematically applying WHO criteria to the polyp findings.

LIMITATIONS

Retrospective study.

CONCLUSIONS

SPS was common in a cohort of patients with large sessile colorectal polyps, and it was frequently unrecognized. These data suggest the need for better detection of serrated lesions, better awareness of SPS, and more consistent application of SPS criteria to the polyp findings of individual patients.

Serrated polyposis syndrome: Molecular, pathological and clinical aspects

Hyperplastic polyps have traditionally been considered not to have malignant potential. New pathological classification of serrated polyps and recent discoveries about the serrated pathway of carcinogenesis have revolutionized the concepts and revitalized the research in this area. Until recently, it has been thought that most colorectal cancers arise from conventional adenomas via the traditional tumor suppressor pathway initiated by a mutation of the APC gene, but it has been found that this pathway accounts for only approximately 70%-80% of colorectal cancer (CRC) cases. The majority of the remaining colorectal cancer cases follow an alternative pathway leading to CpG island methylator phenotype carcinoma with BRAF mutation and with or without microsatellite instability. The mechanism of carcinomas arising from this alternative pathway seems to begin with an activating mutation of the BRAF oncogene. Serrated polyposis syndrome is a relatively rare condition characterized by multiple and/or large serrated polyps of the colon. Clinical characteristics, etiology and relationship of serrated polyposis syndrome to CRC have not been clarified yet. Patients with this syndrome show a high risk of CRC and both sporadic and hereditary cases have been described. Clinical criteria have been used for diagnosis and frequent colonoscopy surveillance should be performed in order to prevent colorectal cancer. In this review, we try to gather new insights into the molecular pathogenesis of serrated polyps in order to understand their possible clinical implications and to make an approach to the management of this syndrome.

Cancer risks for relatives of patients with serrated polyposis

OBJECTIVES

Serrated polyposis (hyperplastic polyposis) is characterized by multiple polyps with serrated architecture in the colorectum. Although patients with serrated polyposis are known to be at increased risk of colorectal cancer (CRC) and possibly extracolonic cancers, cancer risk for their relatives has not been widely explored. The aim of this study was to estimate the risks of CRC and extracolonic cancers for relatives of patients with serrated polyposis.

METHODS

A cohort of the 1,639 first- and second-degree relatives of 100 index patients with serrated polyposis recruited regardless of a family history of polyps or cancer from genetic clinics in Australia, New Zealand, Canada, and the USA, were retrospectively analyzed to estimate the country-, age-, and sex-specific standardized incidence ratios (SIRs) for relatives compared with the general population.

RESULTS

A total of 102 CRCs were observed in first- and second-relatives (SIR 2.25, 95% confidence interval (CI) 1.75-2.93; P<0.001), with 54 in first-degree relatives (SIR 5.16, 95% CI 3.70-7.30; P<0.001) and 48 in second-degree relatives (SIR 1.38, 95% CI 1.01-1.91; P=0.04). Six pancreatic cancers were observed in first-degree relatives (SIR 3.64, 95% CI 1.70-9.21; P=0.003). There was no statistical evidence of increased risk for cancer of the stomach, brain, breast, or prostate.

CONCLUSIONS

Our finding that relatives of serrated polyposis patients are at significantly increased risk of colorectal and pancreatic cancer adds to the accumulating evidence that serrated polyposis has an inherited component.

Hyperplastic Polyposis Syndrome Identified with a BRAF Mutation

Hyperplastic polyposis syndrome (HPS) is a rare condition characterized by the presence of numerous hyperplastic polyps (HPs) in the colon and rectum. Patients with HPS have an increased risk of colorectal cancer. This link is associated with gene mutations, especially B type Raf kinase (BRAF). However, a case of HPS associated with gene mutations has seldom been reported in Korea. Here, we describe a case of HPS in which a BRAF mutation was present in a 34-year-old woman. She had more than 110 HPs in the stomach and colorectum, which we removed. All of the polyps were diagnosed histologically as HPs, and no adenomatous or malignant changes were noted. We performed a BRAF and K-ras mutation analysis as well as a microsatellite analysis on the resected colon polyps. BRAF mutations were found in the resected colon polyps, but there was no evidence of K-RAS mutation or microsatellite instability.

Serrated polyposis syndrome and the role of serrated polyps in colorectal cancer development

SUMMARY Serrated polyposis syndrome is characterized by the presence of multiple colorectal serrated polyps and is associated with an increased colorectal cancer risk. The mixture of distinct precursor lesion types and malignancies in serrated polyposis syndrome provides a unique model to study the recently proposed serrated neoplasia pathway. This pathway involves the progression of serrated polyps, that is, hyperplastic polyps, sessile serrated adenoma/polyps and/or traditional serrated adenomas, to colorectal cancer. The early genetic events of this route, as currently identified, are BRAF or KRAS mutations and an enhanced CPG island methylation status of multiple genes. There is evidence to suggest that a proportion of sporadic colorectal cancers originate from serrated polyps, which encompass molecular sequences of events such as hypermethylation of different genes and BRAF mutations. This review discusses the characteristics and clinical relevance of serrated polyps and provides an overview of the clinical aspects and treatment of serrated polyposis syndrome.

A serrated colorectal cancer pathway predominates over the classic WNT pathway in patients with hyperplastic polyposis syndrome

Hyperplastic polyposis syndrome (HPS) is characterized by the presence of multiple colorectal serrated polyps and is associated with an increased colorectal cancer (CRC) risk. The mixture of distinct precursor lesion types and malignancies in HPS provides a unique model to study the canonical pathway and a proposed serrated CRC pathway in humans. To establish which CRC pathways play a role in HPS and to obtain new support for the serrated CRC pathway, we assessed the molecular characteristics of polyps (n = 84) and CRCs (n = 19) in 17 patients with HPS versus control groups of various sporadic polyps (n = 59) and sporadic microsatellite-stable CRCs (n = 16). In HPS and sporadic polyps, APC mutations were exclusively identified in adenomas, whereas BRAF mutations were confined to serrated polyps. Six of 19 HPS CRCs (32%) were identified in a serrated polyp. Mutation analysis performed in the CRC and the serrated component of these lesions showed identical BRAF mutations. One HPS CRC was located in an adenoma, both components harboring an identical APC mutation. Overall, 10 of 19 HPS CRCs (53%) carried a BRAF mutation versus none in control group CRCs (P = 0.001). Six BRAF-mutated HPS CRCs (60%) were microsatellite unstable owing to MLH1 methylation. These findings provide novel supporting evidence for the existence of a predominant serrated CRC pathway in HPS, generating microsatellite-stable and microsatellite-instable CRCs.

The genomics of colorectal cancer: state of the art

The concept of the adenoma-carcinoma sequence, as first espoused by Morson et al. whereby the development of colorectal cancer is dependent on a stepwise progression from adenomatous polyp to carcinoma is well documented. Initial studies of the genetics of inherited colorectal cancer susceptibility concentrated on the inherited colorectal cancer syndromes, such as Familial Adenomatous Polyposis (FAP) and Lynch Syndrome (also known as HNPCC). These syndromes, whilst easily characterisable, have a well understood sequence of genetic mutations that predispose the sufferer to developing colorectal cancer, initiated for example in FAP by the loss of the second, normal allelle of the tumour supressor APC gene. Later research has identified other inherited variants such as MUTYH (MYH) polyposis and Hyperplastic Polyposis Syndrome. Recent research has concentrated on the pathways by which colorectal adenomatous polyps not due to one of these known inherited susceptibilities undergo malignant transformation, and determination of the types of polyps most likely to do so. Also, why do individuals in certain families have a predisposition to colorectal cancer. In this article, we will discuss briefly the current state of knowledge of the genomics of the classical inherited colorectal cancer syndromes. We will also discuss in detail the genetic changes in polyps that undergo malignant transformation as well as current knowledge with regards to the epigenomic changes found in colorectal polyps.

[Colorectal polyposis syndrome: a guide to diagnosis]

Biopsies and resection specimens of the gastrointestinal tract are a major part of the routine workload in many histopathology departments, whereby polypoid lesions are generally the main focus. In addition to distinguishing non-neoplastic from neoplastic polyps and evaluating the grade of dysplasia of the latter, the pathologist should always consider the possibility of an underlying polyposis syndrome. Not only have additional hereditary polyposis syndromes been identified in recent years due to a better understanding of their genetic and epigenetic alterations but also knowledge on well known polyposes has improved, leading to subtyping of various forms according to their different genotype. It is essential for the histopathologist to understand that the conventional histomorphology of individual polyps combined with information on the number and distribution of these lesions and clinical data can provide clues regarding a possible hereditary background. Therefore, the correct histological assessment of polyps is not just about getting the diagnosis right, it might also lead to genetic screening of family members and spouses.

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.

Investigating the potential role of genetic and epigenetic variation of DNA methyltransferase genes in hyperplastic polyposis syndrome

Background

Hyperplastic Polyposis Syndrome (HPS) is a condition associated with multiple serrated polyps, and an increased risk of colorectal cancer (CRC). At least half of CRCs arising in HPS show a CpG island methylator phenotype (CIMP), potentially linked to aberrant DNA methyltransferase (DNMT) activity. CIMP is associated with methylation of tumor suppressor genes including regulators of DNA mismatch repair (such as MLH1, MGMT), and negative regulators of Wnt signaling (such as WIF1). In this study, we investigated the potential for interaction of genetic and epigenetic variation in DNMT genes, in the aetiology of HPS.

Methods

We utilized high resolution melting (HRM) analysis to screen 45 cases with HPS for novel sequence variants in DNMT1, DNMT3A, DNMT3B, and DNMT3L. 21 polyps from 13 patients were screened for BRAF and KRAS mutations, with assessment of promoter methylation in the DNMT1, DNMT3A, DNMT3B, DNMT3L MLH1, MGMT, and WIF1 gene promoters.

Results

No pathologic germline mutations were observed in any DNA-methyltransferase gene. However, the T allele of rs62106244 (intron 10 of DNMT1 gene) was over-represented in cases with HPS (p<0.01) compared with population controls. The DNMT1, DNMT3A and DNMT3B promoters were unmethylated in all instances. Interestingly, the DNMT3L promoter showed low levels of methylation in polyps and normal colonic mucosa relative to matched disease free cells with methylation level negatively correlated to expression level in normal colonic tissue. DNMT3L promoter hypomethylation was more often found in polyps harbouring KRAS mutations (p = 0.0053). BRAF mutations were common (11 out of 21 polyps), whilst KRAS mutations were identified in 4 of 21 polyps.

Conclusions

Genetic or epigenetic alterations in DNMT genes do not appear to be associated with HPS, but further investigation of genetic variation at rs62106244 is justified given the high frequency of the minor allele in this case series.

Defining phenotypes and cancer risk in hyperplastic polyposis syndrome

BACKGROUND

Hyperplastic polyposis syndrome is a rare syndrome of colorectal cancer predisposition. Patterns of inheritance of hyperplastic polyposis syndrome are not obvious and the clinical definition is relatively arbitrary. We hypothesize that there are multiple phenotypes included in what is currently called hyperplastic polyposis syndrome. We performed this review of a large series of patients who presented with multiple serrated polyps to look for clinical patterns that may confirm our hypothesis.

METHODS

Hereditary colorectal cancer, colonoscopy, and clinical databases from a single institution were queried for patients meeting the following criteria: 1) ≥ 20 serrated colorectal polyps; 2) ≥ 5 serrated polyps proximal to the sigmoid; 3) ≥ 2 serrated polyps ≥ 10 mm in size; 4) any serrated polyps in a person with at least one first-degree relative who has hyperplastic polyposis syndrome. Records were reviewed for demographics, polyp details, and personal or family history of colorectal extracolonic malignancy.

RESULTS

One-hundred fifteen patients were included. Median age at diagnosis was 62 years and 56% were male. Ninety-seven percent were white. Twenty-five percent of patients had a personal history and 38% had a family history of colorectal cancer. Twenty-eight percent of patients had a personal history and 54% had a family history of extracolonic cancer. Phenotype analysis identified 3 patterns: relatively few large, right-sided polyps (n = 55), many small left-sided polyps (n = 18), and a combination of both left- and right-sided polyps (n = 42). The right-sided phenotype had more sessile serrated polyps and tended to develop colorectal cancer at a younger age.

CONCLUSIONS

There are at least 3 different but overlapping clinical phenotypes within hyperplastic polyposis. Recognizing this clinical heterogeneity is important in defining underlying genetic causes.

A significant number of sessile serrated adenomas might not be accurately diagnosed in daily practice

BACKGROUND/AIMS

The diagnosis of hyperplastic polyps (HPs) may involve a conglomeration of subgroups of serrated polyps. The diagnosis of HPs may therefore be revisited if this is sessile serrated adenoma (SSA). The aim of this study was to determine clinically and endoscopically relevant information associated with reclassification to SSA.

METHODS

After reviewing the data from 1,372 patients who underwent colonoscopic polypectomy, 49 HPs larger than 10 mm were analyzed in this study. Two gastrointestinal pathologists reclassified each of the original 49 HPs as conventional HPs, SSAs, and others.

RESULTS

Among the 49 initially diagnosed HPs, 18.4% were reclassified into SSAs or mixed polyps. Overall architectural features were useful for the diagnosis of SSA, but cytological features were less useful. The patient and polyp characteristics did not differ between HPs with and without reclassification of the initial pathological diagnosis.

CONCLUSIONS

A significant number of SSAs might not be accurately diagnosed in daily clinical practice without any predilection for size, shape, and location. Therefore, when large HPs are diagnosed in clinical practice, it is necessary for physicians to have greater awareness of the diagnosis of SSA and to individualize subsequent surveillance.

Risk factors: Hyperplastic polyposis syndrome and risk of colorectal cancer

Hyperplastic polyposis syndrome is a widely accepted, but poorly understood, risk factor for colorectal cancer. A recent report has laid the foundations for improving the management of patients with this enigmatic disorder by identifying the features associated with colorectal cancer risk, as well as estimating the magnitude of this risk.

Lessons from Lynch syndrome: a tumor biology-based approach to familial colorectal cancer

Colorectal cancer (CRC) develops within precursor lesions in the single-celled epithelial lining of the gut. The two most common epithelial lesions are the adenoma and the serrated polyp. CRC is also one of the most familial of the common cancers, and just as there are syndromes associated with increased risk of CRC arising in adenomas, there are also syndromes with increased CRC risk associated with serrated polyps. In this article, we describe the features of such a syndrome, familial serrated neoplasia, which distinguish it from the well-characterized condition Lynch syndrome (or hereditary nonpolyposis CRC), and show that the molecular pathology of tumors forms the basis for this distinction. Lynch syndrome CRC arises almost exclusively within adenomatous precursor lesions, in contrast with familial serrated neoplasia where at least half of the cancers develop in serrated polyps. Finally, rare families exist in which both conditions segregate independently, producing a difficult diagnostic picture.

Hyperplastic polyposis syndrome is associated with cigarette smoking, which may be a modifiable risk factor

OBJECTIVES

Hyperplastic polyposis syndrome (HPS) confers an increased risk of colorectal cancer and is difficult to manage clinically. Because both polyps and resultant cancers display the CpG island methylator phenotype and mutation of the BRAF oncogene, and because sporadic cancers with these characteristics are associated with cigarette smoking, we hypothesized that cigarette smoking may predispose to the development of HPS.

METHODS

This was a case-control study with two independent control series conducted at a tertiary hospital in Brisbane, Queensland, Australia. Cases comprised patients with HPS (n=32) recruited through the database of the Queensland Familial Bowel Registry, who satisfied the World Health Organization international classification for HPS. Cases were compared with colonoscopy controls (n=298) defined as consecutive patients undergoing colonoscopy for clinical indications, who were free from polyps. We also compared cases with a second set of population controls (n=645) selected at random from a population register serving the catchment area for cases. This was an observational study, and all participants completed a questionnaire to obtain a comprehensive smoking history.

RESULTS

The prevalence rate of current smoking was 47% in HPS patients, 17% in colonoscopy controls, and 12% in population controls. HPS patients were significantly more likely to be current smokers than were either colonoscopy controls (odds ratio (OR)=8.3, 95% confidence interval (CI): 3.0-22.9) or population controls (OR=12.7, 95% CI: 4.9-33.1).

CONCLUSIONS

Cigarette smoking is strongly associated with HPS, thus suggesting that smoking exposure may increase the expression of this condition. Further studies should examine the possible benefits of quitting smoking in HPS patients.

Phenotypic diversity in patients with multiple serrated polyps: a genetics clinic study

OBJECTIVE

Hyperplastic polyposis is a colonic polyposis condition of unknown aetiology. The purpose of this study was to examine the spectrum of phenotypic variation in patients with multiple serrated polyps as a basis for gene discovery.

METHODS

One hundred and twenty-six patients with multiple (> or = 5) serrated polyps were recruited to the study. Polyp counts were extracted from histology and colonoscopy reports. Ethnicity was self-reported. Family history of cancer data were derived from pedigrees. Ascertainment status was classified as either index case or identified by screening.

RESULTS

The average reported polyp count was 39. Patients with highest polyp numbers were more likely to be male (P = 0.02). Colorectal cancer (CRC) was identified in 49 of 119 patients (41%) and 28% of these patients had multiple CRC. Young onset patients had higher polyp numbers (P = 0.03) and were more likely to have their CRC in the distal colon (P = 0.02). CRC was significantly associated with the presence of adenomas (P = 0.03). Patients were divided into moderate polyposis (5-79 serrated polyps) and dense polyposis (80 or more) categories. The dense polyposis category was associated with a lack of family history for CRC (P = 0.034) and male gender (P = 0.014), independent of ascertainment status and recruitment site.

CONCLUSION

Multiple serrated polyps were associated with an increased personal risk of CRC. A subset of patients with the highest polyp numbers was more likely to be male and to have no family history of CRC. This result suggests heterogeneous modes of inheritance and has implications for studies investigating the genetic basis of multiple serrated polyps.