Hyperplastic-adenomatous polyposis syndrome

Long-Term Incidence of Advanced Colorectal Neoplasia in Patients with Serrated Polyposis Syndrome: Experience in a Single Academic Centre

Simple Summary

Serrated polyposis syndrome is characterized by the development of large and/or multiple serrated polyps throughout the colorectum and is associated with an increased risk of colorectal cancer (CRC). Even though CRC incidence is low under adequate endoscopic follow-up, a substantial risk of advanced neoplasia (AN) has been described. Nevertheless, very few studies have focused on long-term surveillance. The main aim of this study was to evaluate the incidence of AN in a single-centre cohort followed over 10 years. Within endoscopic surveillance we did not find any CRC and we observed that five-year cumulative incidences of AN were much lower than in other studies. However, a significant reduction of these incidences during follow-up was not proven. Individuals at higher risk of AN were those who fulfilled both 2010 WHO criteria I and III. Our results suggest that at least patients at lower risk might benefit from the extension of surveillance intervals.

Abstract

Serrated polyposis syndrome (SPS) implies a slightly elevated risk of colorectal cancer (CRC) during endoscopic follow-up, but its natural course is still not well known. The main objective of this study was to describe the long-term risk of developing advanced neoplasia (AN) in these patients. Until October 2020, individuals who fulfilled 2010 WHO criteria I and/or III for SPS were retrospectively recruited. We selected those under endoscopic surveillance after resection of all lesions >3 mm in a high-quality colonoscopy. We excluded patients with total colectomy at diagnosis and those with any interval between colonoscopies >3.5 years. We defined AN as advanced serrated polyp (≥10 mm and/or with dysplasia), advanced adenoma, or CRC. In 109 patients, 342 colonoscopies were performed (median = 3, median interval = 1.8 years) during a median follow-up after colonic clearance of 5.0 years. Five-year cumulative incidences of AN were 21.6% globally, and 5.6%, 10.8%, and 50.8% in patients who fulfilled criterion I, III, and both, respectively (p < 0.001). No CRC was diagnosed and only 1 (0.9%) patient underwent surgery. In conclusion, cumulative incidences of AN could be lower than previously described, at least in patients who fulfil the 2010 WHO criterion III alone. Therefore, low-risk individuals might benefit from less stringent surveillance.

Molecular pathways in colorectal cancer

Colorectal cancer (CRC) is the second most common newly diagnosed cancer and accounts for the second highest number of cancer related deaths in Australia, the third worldwide and of increasing importance in Asia. It arises through cumulative effects of inherited genetic predispositions and environmental factors. Genomic instability is an integral part in the transformation of normal colonic or rectal mucosa into carcinoma. Three molecular pathways have been identified: these are the chromosomal instability (CIN), the microsatellite instability (MSI), and the CpG Island Methylator Phenotype (CIMP) pathways. These pathways are not mutually exclusive, with some tumors exhibiting features of multiple pathways. Germline mutations are responsible for hereditary CRC syndromes (accounting for less than 5% of all CRC) while a stepwise accumulation of genetic and epigenetic alterations results in sporadic CRC. This review aims to discuss the genetic basis of hereditary CRC and the different pathways involved in the process of colorectal carcinogenesis.

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.

Serrated polyps of the colon

Until recently, colonic polyps were traditionally classified as either hyperplastic or adenomatous, and only the latter were believed to have the potential to progress to carcinoma. However, it is now appreciated that a subset of serrated polyps also appear to have malignant potential. Serrated polyps are a heterogeneous group of colon polyps that include hyperplastic polyps, sessile serrated adenomas (SSAs), traditional serrated adenomas, and mixed polyps. Insights into these polyps were derived, in part, from studies of patients with the hyperplastic polyposis syndrome. SSAs show a predilection for the right colon, have a distinct histology, and their molecular genetic profile has recently been linked to a pathway for colon tumorigenesis that is characterized by microsatellite instability. Based upon available evidence, it is recommended that patients with serrated adenomas undergo colonoscopic follow-up at the same frequency as for conventional adenomas. It is important that physicians are aware of serrated polyps, particularly serrated adenomas and their relationship to colon cancer, and their proper clinical management.

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.

Role of the serrated pathway in colorectal cancer pathogenesis

The "serrated neoplastic pathway" describes the progression of serrated polyps, including sessile serrated adenomas and traditional serrated adenomas, to colorectal cancer. The recognition of this pathway during the last 15 years has led to a paradigm shift in our understanding of the molecular basis of colorectal cancer and significant changes in clinical practice. These findings are particularly relevant to prevention of interval cancers through colonoscopy surveillance programs-an important issue for colonoscopists. In the past, all serrated polyps were classified simply as hyperplastic polyps and were considered to have no malignant potential. Reappraisal of this view was largely driven by increasing recognition of the malignant potential of hyperplastic polyposis.

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.

Less common colorectal cancer predisposition syndromes

A variety of syndromes confer increased risk for intestinal polyp development, outside the more commonly occurring syndromes. Each of these uncommon syndromes predispose to pathognomonic histologies that are uncommonly observed. Accurate diagnosis of these syndromes is contingent on higher-level pathology review, evaluation of signs and symptoms beyond sole consideration of the polyps, and collection of a detailed family history. When a genetic mutation can be identified in the proband, the management of intestinal and extra-intestinal cancer screening can be more appropriately tailored.

Colorectal polyposes: from phenotype to diagnosis

The colorectal polyposes are uncommon and frequently present diagnostic difficulties. Although the final diagnostic arbiter is the demonstration of a germline mutation, this may not always be demonstrable, and some forms of colorectal polyposis have no known genetic basis. Therefore, an accurate description of the phenotype by the pathologist is central to the establishment of a working diagnosis. This can direct the search for the underlying genetic cause (if any) and is also essential for establishing the magnitude of risk of colorectal malignancy for the patient and the patient's relatives. The pathologist may be provided with only a small and selected sample of endoscopically resected polyps or with prodigious numbers of polyps (too many to sample) when receiving a surgical specimen. Each type of polyposis presents its own particular diagnostic problems that may relate to polyp numbers, gross recognition of small or flat polyps, incomplete development of the full phenotype at the stage of investigation, and the histological classification of unusual or mixed polyps. The aim of this review is to highlight the principles and pitfalls in achieving a comprehensive description of the various types of colorectal polyposis, including classical FAP, attenuated FAP, MUTYH- (formerly MYH-) associated polyposis (MAP), other presentations of multiple adenomas, Peutz-Jeghers syndrome (P-JS), juvenile polyposis syndrome (JPS), Cowden syndrome (CS), hereditary mixed polyposis syndrome (HMPS), and hyperplastic polyposis syndrome (HPS).

Gastrointestinal polyposes: clinical, pathological and molecular features

This article focuses mainly on noninflammatory epithelial polyposes, particularly the diagnostically important morphological and molecular features of the more recently recognized and/or more poorly understood conditions. One of the most important, but often neglected, of these is hyperplastic polyposis.

Molecular classification and genetic pathways in hyperplastic polyposis syndrome

Hyperplastic Polyposis (HPPS) is a poorly characterized syndrome that increases colorectal cancer (CRC) risk. We aimed to provide a molecular classification of HPPS. We obtained 282 tumours from 32 putative HPPS patients with >or= 10 hyperplastic polyps (HPs); some patients also had adenomas and CRCs. We found no good evidence of microsatellite instability (MSI) in our samples. The epithelium of HPs was monoclonal. Somatic BRAF mutations occurred in two-thirds of our patients' HPs, and KRAS2 mutations in 10%; both mutations were more common in younger cases. The respective mutation frequencies in a set of 'sporadic' HPs were 18% and 10%. Importantly, the putative HPPS patients generally fell into two readily defined groups, one set whose polyps had BRAF mutations, and another set whose polyps had KRAS2 mutations. The most plausible explanation for this observation is that there exist different forms of inherited predisposition to HPPS, and that these determine whether polyps follow a BRAF or KRAS2 pathway. Most adenomas and CRCs from our putative HPPS patients had 'classical' morphology and few of these lesions had BRAF or KRAS2 mutations. These findings suggest that tumourigenesis in HPPS does not necessarily follow the 'serrated' pathway. Although current definitions of HPPS are sub-optimal, we suggest that diagnosis could benefit from molecular analysis. Specifically, testing BRAF and KRAS2 mutations, and perhaps MSI, in multiple polyps could help to distinguish HPPS from sporadic HPs. We propose a specific model which would have diagnosed five more of our cases as HPPS compared with the WHO clinical criteria.

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

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

[Emerging concepts in colorectal serrated polyps]

Colorectal serrated polyps are heterogeneous epithelial lesions characterized by a serrated architecture. They include the classical hyperplastic polyps and the much rarer serrated adenomas and mixed polyps. Whereas serrated adenomas are composed of an unequivocal adenomatous epithelium with architectural serrated, mixed polyps include two separate hyperplastic and adenomatous components. During the past few years, another type of serrated polyp with only very subtle proliferation abnormalities has been described. These atypical serrated polyps may occur either sporadically or in the context of colorectal polyposis. Despite their close resemblance to traditional hyperplastic polyps, some authors argued that they should be regarded as authentically neoplastic lesions and have proposed to call them "sessile serrated adenomas". Their malignant potential requires their removal when discovered during colonoscopy. This article reviews the histological features, the endoscopic appearance, the natural history and the molecular phenotype of the different categories of serrated polyps and introduces the concept of "serrated neoplastic pathway" in the development of colorectal cancer.

Hyperplastic polyposis syndrome: phenotypic presentations and the role of MBD4 and MYH

BACKGROUND & AIMS

Hyperplastic polyposis syndrome (HPS) is defined phenotypically with multiple, large and/or proximal hyperplastic polyps. There is no known germ-line predisposition. We aimed to characterize the clinicopathologic features of 38 patients with HPS and explore the role of germ-line mutations in the base excision repair genes MBD4 and MYH.

METHODS

Utilizing clinical databases of The Royal Melbourne Hospital Bowel Cancer Surveillance Service and the Familial Cancer Clinic, 38 patients with HPS were recruited. The patients were analyzed for age at first diagnosis, features of hyperplastic polyposis, family histories of polyposis and colorectal cancer (CRC), coexisting adenomas, serrated adenomas, incidence of CRC, and microsatellite instability in the tumours. Mutation analysis of MBD4 and MYH were performed.

RESULTS

Serrated adenomas were common (26%), and 19 (50%) of the 38 patients had a first-degree relative with CRC. Family history of HPS was uncommon, with only 2 cases found. Ten patients developed CRC, and 3 required surgery for polyposis. No pathogenic mutations in MBD4 were detected in the 27 patients tested, but 6 single nucleotide polymorphisms of uncertain functional significance were identified. Pathogenic biallelic MYH mutations were detected in 1 patient.

CONCLUSIONS

Mutations in MBD4 are unlikely to be implicated in HPS; MYH mutations should be studied, especially when adenomas occur in the same patient. The clinical, histopathologic, and molecular findings of this study should contribute to our understanding of HPS and its relationship to the serrated neoplasia pathway.

Preoperative evaluation of colorectal cancer

Surgery is a primary modality for the treatment of patients with colorectal cancer. Before any surgical therapy, patients diagnosed with colorectal cancer require an evaluation. This preoperative evaluation can be used to assess the patient's risk associated with surgery, plan the surgical resection, and stage the patient's cancer. Staging of the cancer preoperatively is primarily of concern in rectal cancer patients. This article focuses on the elective surgical setting and the recommended preoperative evaluation of patients who have been diagnosed with colorectal cancer.

A scoring system for the strength of a family history of colorectal cancer

BACKGROUND

Family history of colorectal cancer is associated with an increased risk for the disease, although there are many combinations of family history that are hard to correlate with risk status. A scoring system for family history of colorectal cancer was designed to make risk more readily quantifiable.

METHODS

A colonoscopy database was used to test the following points system: each first-degree relative with colorectal cancer = 3 points; each second-degree relative with colorectal cancer = 1 point. Families with one or more first-degree relative affected under 50 years of age = an extra 3 points. Families with one or more second-degree relative affected under 50 years of age = an extra 1 point. Families with multiple relatives on the same side of the family = an extra 3 points (first-degree relatives), 1 point (second-degree relatives), or 2 points (first-degree and second-degree relatives). Points were added and categories defined as follows: low risk, 1 to 4 points; medium risk, 5 to 7 points; high risk, 8 to 10 points; very high risk, >10 points. A control group of average-risk patients having screening colonoscopy was used. Categories were compared in number of adenomas, hyperplastic polyps, and cancers.

RESULTS

The records of 992 patients were used to test the system. Mean adenomas per patient per group were 0.4 for controls, 1.0 for low risk, 1.0 for medium risk, 1.7 for high risk, and 1.7 for very high risk. Cancers per group were 2 of 196 for controls, 8 of 513 for low risk, 3 of 171 for medium risk, 3 of 84 for high risk, and 1 of 28 for very high risk. The score categories were combined to produce revised risk levels of low (score 1 to 7) and high (>7). Average adenomas per patient in the revised categories were 0.4 (control), 1.0 (low risk), and 1.7 (high risk). The odds ratio of having one to two adenomas was 1.73 (1.19-2.50, 95% confidence limits) in the low-risk group and 2.39 (1.41-4.01) in the high-risk group. Odds ratios for having three or more adenomas were 5.70 (2.44-13.32) in the low-risk group and 10.35 (3.97-26.97) in the high-risk group.

CONCLUSION

In the two-category system proposed here of quantifying familial risk of colorectal cancer, patients having less than 8 points were at low risk and those with 8 or more were at high risk. Surveillance and chemoprevention protocols can be designed through use of these risk categories. A scoring system for family history of colorectal cancer can make risk assessment easier and facilitate both collaborative studies and patient triage into appropriate screening programs.

Genetics of hereditary colorectal cancer

Genetic factors can dramatically influence the risk of colorectal cancer, and the molecular bases of many hereditary colorectal cancer syndromes, including familial adenomatous polyposis (FAP), attenuated FAP (AFAP), and hereditary nonpolyposis colorectal cancer (HNPCC) have been elucidated. Additional syndromes continue to be defined as new genes, including MYH , are linked to the development of colonic polyps and cancer. The risks of colorectal cancer are variable and depend on the specific germline alterations. Some mutations are associated with a 100% lifetime risk of developing cancer, while others are associated with only a mild increase in risk. Although there are overlapping clinical features in many of these syndromes, they can be distinguished by the age at cancer diagnosis, inheritance pattern, number and distribution of polyps, specific histologic features of the cancers, and the presence of distinctive extracolonic features. The introduction and refinement of genetic testing has provided a new and invaluable tool for the diagnosis and assessment of cancer risk for suspected cases of hereditary colon cancer.

Hyperplastic polyposis and the risk of colorectal cancer

PURPOSE

Hyperplastic polyps are usually considered to be an innocent finding with little or no potential to progress to colorectal cancer. However, recent literature suggests that some of these polyps may be morphologically and genetically distinct and lead to microsatellite unstable colorectal cancers. The purpose of this study was to define the cancer risk associated with hyperplastic polyposis.

METHODS

All patients with hyperplastic polyposis diagnosed by a single colorectal surgeon at a university hospital were followed prospectively. The diagnosis of hyperplastic polyposis was made by the presence of more than 20 hyperplastic polyps distributed throughout the colon and/or a hyperplastic polyp at least 1 cm in size in diameter in the right colon. Patient demographics, family history, size, location, and distribution of polyps and the development of colorectal cancer were noted.

RESULTS

Thirteen patients who met the criteria for hyperplastic polyposis were identified and followed prospectively. All of these patients had at least 30 polyps distributed throughout the colon, often > 100. Nine of 13 also had a hyperplastic polyp at least 1 cm in size, usually in the right colon. Of particular note, 7 of 13 patients (54 percent) were diagnosed with colorectal cancer during the study period. Four had cancer on initial diagnosis and three patients developed cancer despite frequent colonoscopic surveillance. Five of seven colorectal cancers were located in the right colon.

CONCLUSIONS

Patients with hyperplastic polyposis are at high risk for colorectal cancer. Failure to identify this subset of patients could have dire consequences.

Phenotypic characteristics and risk of cancer development in hyperplastic polyposis: case series and literature review

OBJECTIVES

Hyperplastic polyposis (HP) is a poorly understood condition. The aim of this study is to describe the phenotype and the risk of cancer in HP.

METHODS

Patients with HP, as defined by the WHO International Classification, were identified through the University of Utah and the Huntsman Cancer Institute databases. Family history was retrieved when possible.

RESULTS

Fifteen patients were identified (10 M, 5 F) with a mean age at diagnosis of 52.6 +/- 16.4 yr (18-71). Sixty-five colonoscopies were performed (2-11 per person). A median of 90 polyps (16-210) per person and 15 polyps (range, 0-100) per procedure were reported. The median follow-up was 33 months (3-133); no cancer occurred during this period. Polyps were more frequent in the distal than the proximal colon (74%vs 26%; p < 0.001). The median polyp size was 4 mm (1-40 mm). Fifty-one hyperplastic polyps >10 mm were identified in 10 patients (38 proximal, 13 distal; p= 0.089). Forty-eight adenomas were found in 11 patients and were uniformly distributed. Serrated adenomas (n = 3) were found in one patient. A unique patient had 20 large hyperplastic polyps, 24 adenomas, 3 serrated adenomas, and 118 hyperplastic polyps. None of the patients had a first-degree relative with colon cancer.

CONCLUSIONS

In HP, hyperplastic polyps are more frequently distal colonic, and vary greatly in size and number. Most patients also develop adenomas that are distributed throughout the colon. No cancers developed within 3 yr of follow-up. Colonoscopic surveillance at intervals of 1-3 yr, depending upon the number and size of both adenomatous and hyperplastic polyps, appears prudent.

Simple and complex genetics of colorectal cancer susceptibility

There are several hereditary conditions associated with an increased risk of colorectal cancer (CRC). These include well-characterized autosomal dominant syndromes, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC). A novel autosomal recessive form of FAP, caused by mutations in the base excision repair gene MYH, has recently been recognized. This discovery has provided further evidence for the importance of DNA repair mechanisms in CRC development, already documented by the involvement of the mismatch repair in HNPCC. Additional CRC-predisposing conditions, such as hyperplastic polyposis and hereditary mixed polyposis syndrome, are being outlined. Heterogeneity of genetic mechanisms has important consequences for counseling and surveillance in hereditary CRC. Nevertheless, classical mendelian conditions represent only a minor share of the total CRC population burden. Alleles of the same genes that are involved in hereditary syndromes might also act as low penetrance variants, as shown for APC 1307K in the Ashkenazi. However, the level of complexity of multifactorial CRC is such that current tools appear inadequate to pinpoint all the involved components. A combination of different strategies, including careful clinical observation, analysis of homogeneous patient populations, and critical evaluation of data derived from experimental models, along with methodological improvements in nucleic acid analysis, will probably be necessary to unravel the basis of nonmendelian CRC. Once this is achieved, it will be possible to realize the ultimate goal of targeted CRC prevention, with the adoption of measures tailored according to individual risk levels. .

Management of Portuguese patients with hyperplastic polyposis and screening of at-risk first-degree relatives: a contribution for future guidelines based on a clinical study

BACKGROUND

Hyperplastic polyposis (HP) is a rare condition characterized by the presence of multiple hyperplastic polyps in the colon, which has been associated to an increased risk of colorectal cancer (CRC). Guidelines for management of this disease remain, so far, undefined.

AIMS

To evaluate, in symptomatic patients with HP, phenotypic characteristics as well as results of a screening program in their at-risk first-degree relatives.

PATIENTS

Pedigree information and clinical and endoscopic data of 14 patients with HP was studied. SEVENTEEN AND METHODS: at-risk first-degree relatives from six families were also invited to perform screening colonoscopy.

RESULTS

Twelve of fourteen (86%) patients had fewer than 100 colorectal polyps. Polyps' sizes ranged from 2 to 25 mm and were uniformly distributed through the whole colon in 43% of the patients. Hyperplastic polyps predominated, but 11/14 (79%) patients also harbored serrated as well as classic adenomatous polyps. CRC was present in 6/14 (43%) of the patients at the time of diagnosis. Familial history of CRC/polyps was positive in 6/12 (50%) of cases. Colonoscopy in at-risk relatives disclosed polyps in 10/17 (59%) of cases with at least one additional patient having criteria for HP.

CONCLUSIONS

Although small, this series demonstrates that a high level of suspicion is needed to diagnose the HP syndrome, in which serrated adenomas seem to be the hallmark. Although an elevated percentage of CRC was observed in this series of symptomatic patients with HP, prospective studies in asymptomatic individuals are needed to clearly quantify the risk of CRC in patients with HP. Because familial aggregation of HP was present in 3/12 (25%) of kindreds, screening colonoscopy should be offered to first-degree relatives.

Benign Fibroblastic Polyps of the Colon

Mesenchymal proliferations presenting as mucosal polyps are relatively uncommon and are represented by gastrointestinal stromal tumors, smooth muscle and neural tumors, and inflammatory fibroid polyps. In this report, we describe the clinicopathologic features of a distinctive type of mucosal polyp composed of cytologically bland spindled cells with fibroblastic features. Fourteen cases with histologic features of"fibroblastic polyps" were identified from our case files from January 2000 to December 2003. The clinical and endoscopic findings were reviewed. Immunohistochemistry using a panel of antibodies (vimentin, smooth muscle actin, desmin, CD31, CD34, Bcl-2, c-Kit, S-100, and epithelial membrane antigen) was performed in all cases, and electron microscopy was performed in two cases. The lesions were solitary in all cases and not associated with an identifiable polyposis syndrome. Associated adenomata and/or hyperplastic polyps at different sites were present in 10 cases and hyperplastic polyps were seen in close association in 3 cases. These polyps were characterized by a monomorphic spindle cell proliferation in the lamina propria, without necrosis or mitotic activity. The lesions were intimately associated with the muscularis mucosae and resulted in wide separation and disorganization of the colonic crypts. Immunohistochemical analysis revealed strong and diffuse positivity for vimentin only. Weak and focal reactivity was noted in 2 cases for CD34 and smooth muscle actin, while staining for other antibodies was negative. Electron microscopy revealed sparse cytoplasmic organelles and many intermediate filaments. The histology and ultrastructural and immunohistochemical findings are suggestive of fibroblastic differentiation of these spindle cells. In summary, these lesions represent a distinctive type of colonic mucosal polyp that should be distinguished from other stromal polyps of the gastrointestinal tract.

Morphologic reappraisal of serrated colorectal polyps

The "hyperplastic polyp" is considered a benign lesion with no malignant potential, whereas "serrated adenoma" is a precursor of adenocarcinoma. The morphologic complexity of the serrated adenoma varies from being clearly adenomatous to being difficult to distinguish from hyperplastic polyp, which creates a need for more detailed morphologic analysis of all serrated polyps. We evaluated 24 morphologic variables in 289 serrated polyps from the colon and rectum. Cluster analysis and discriminant analysis were performed. A subset of polyps was immunostained for hMLH1 and hMSH2. Major differences were found between right-sided and left-sided polyps. A distinct group of serrated polyps with abnormal proliferation was identified throughout the colon and rectum. These polyps demonstrated decreased expression of hMHL1 and hMSH2 compared with polyps with normal proliferation. Left-sided serrated polyps with normal proliferation further clustered into three groups: vesicular cell-type, goblet cell-type, and mucin-poor-type. We recommend evaluation of the localization, size, and morphologic features when serrated polyps are included in colorectal carcinogenesis research. Polyps with abnormal proliferation are similar to the polyps in "hyperplastic polyposis" and, because of their decreased expression of hMLH1 and hMSH2, may be the subset of polyps associated with the development of colorectal carcinoma via the microsatellite instability pathway.

Review article: the non-inherited gastrointestinal polyposis syndromes

The non-inherited gastrointestinal polyposis syndromes represent a group of rare disorders characterized by the presence of multiple, non-adenomatous polyps on the gastrointestinal mucosa occurring in unrelated patients. We present here a review of the clinical and histo- pathological aspects of the syndromes to include the Cronkhite-Canada syndrome, hyperplastic polyposis and lipomatous polyposis. While infrequently encountered, these diseases can have devastating clinical effects that may be aggravated by delays in diagnosis and treatment. Prompt accurate diagnosis and treatment of these uncommon disorders depend on a sound working knowledge of the distinct clinical and pathological features described herein.

Hyperplastic polyposis: association with colorectal cancer

Hyperplastic polyposis is a loosely defined syndrome initially thought not to confer a clinically important predisposition to colorectal cancer. The aim of the current study was to examine the clinical, histologic, and molecular features of a prospective series of cases meeting a strict definition of the condition. Twelve patients were identified, seven of whom had developed colorectal cancer. Most polyps were hyperplastic, but 11 patients also had polyps containing dysplasia as either serrated adenomas. mixed polyps, or traditional adenomas. The mean percentage of dysplastic polyps in patients with cancer was 35%, and in patients without cancer, 11% (p < 0.05). Microsatellite instability (MSI) was present in 3 of 47 hyperplastic polyps and two of eight serrated adenomas. Kras was mutated in 8 of 47 hyperplastic polyps and two of eight serrated adenomas. No polyps showed loss of heterozygosity of chromosomes 5q, 1p, or 18q. Two of seven cancers showed a high level of MSI. It is concluded that hyperplastic polyposis is associated with a high risk of colorectal cancer. Hyperplastic polyps are the dominant type of polyp, but most cases have some dysplastic epithelium. A higher proportion of dysplastic polyps is associated with increased cancer risk. Clonal genetic changes are observed in some hyperplastic polyps and serrated adenomas.

Colorectal carcinomas arising in the hyperplastic polyposis syndrome progress through the chromosomal instability pathway

The hyperplastic polyposis syndrome is characterized by the presence within the colon of multiple large hyperplastic polyps. We describe a case of hyperplastic polyposis syndrome associated with two synchronous carcinomas, one of which arises within a pre-existing hyperplastic lesion. Comparative genomic hybridization was used to determine genetic changes in both carcinomas and several associated hyperplastic lesions. Microsatellite analysis at five loci was performed on carcinomas and representative hyperplastic polyps, and p53 status was analyzed by immunohistochemistry. Both carcinomas showed multiple genetic aberrations, including high level gains of 8q and 13q, and loss of 5q. These changes were not seen in the hyperplastic polyps. Microsatellite instability was not seen in the carcinomas, four separate hyperplastic polyps, the hyperplastic polyp with mild adenomatous change associated with the carcinoma, or a separate serrated adenoma. Allelic imbalance in the cancers at D5S346 and D17S938 suggested allelic loss of both p53 and APC, as well as at the loci D13S263, D13S174, D13S159, and D18S49. An early invasive carcinoma in one hyperplastic polyp stained for p53 protein, but the associated hyperplastic polyp was negative. In this case, neoplastic progression followed the typical genetic pathway of common colorectal carcinoma and occurred synchronously with mutation of p53.