Ki-67, p53, and Bcl-2 expression of serrated adenomas of the colon

Proliferation, apoptosis and their regulatory protein expression in colorectal adenomas and serrated lesions

BACKGROUND

Adenomas and serrated lesions represent heterogeneous sets of early precursors in the colorectum with varying malignant potential. They are often distinguished by their histopathologic differences, but little is known about potential differences in regulation of epithelial proliferation and apoptosis.

METHODS

We conducted a protein expression analysis using tissue microarrays of 625 colorectal adenomas and 142 serrated lesions to determine potential differences in regulation of epithelial proliferation and apoptosis. We quantitated proliferation with Ki-67; apoptosis with activated caspase-3 (CASP3); up- and down-regulators of proliferation with cyclin D1, p16INK2, and p21Cip1; and apoptosis regulators with BAX, BCL2, and survivin. Linear mixed effects models and circos diagrams were used to determine relationships among expression and lesion characteristics.

RESULTS

Adenomas had a significantly higher CASP-3 labeling index (LI) than serrated lesions, resulting in a lower net growth ratio (Ki-67 LI/activated CASP-3 LI, p-value<0.0001). Cyclin D1 LI, p16 LI and p21 LI were lower in adenomas compared to serrated lesions, while expression of both BCL2 and BAX were higher (p <0.001). Among adenomas, cyclin D1 LI and p16 LI levels increased with greater villous component, and the highest BAX expression was detected in adenomas larger than 2 cm (both p<0.0001). Right-sided adenomas had higher CASP3 LI than left colorectal adenomas (p = 0.008). Significant differences in cyclin D1 LI, p21 LI and survivin LI were also observed across histopathologic subtypes of serrated lesions.

CONCLUSIONS

Our findings demonstrate different patterns of regulatory protein expression in adenomas than serrated lesions, especially involving apoptosis. ClinicalTrials.gov Identifier: NCT00272324.

Cecal Tumorigenesis in Aryl Hydrocarbon Receptor-Deficient Mice Depends on Cecum-Specific Mitogen-Activated Protein Kinase Pathway Activation and Inflammation

The aryl hydrocarbon receptor (AhR) is a transcription factor known as a dioxin receptor. Recently, Ahr^-/- mice were revealed to develop cecal tumors with inflammation and Wnt/β-catenin pathway activation. However, whether β-catenin degradation is AhR dependent remains unclear. To determine whether other signaling pathways function in Ahr^-/- cecal tumorigenesis, we investigated histologic characteristics of the tumors and cytokine/chemokine production in tumors and Ahr^-/- peritoneal macrophages. AhR expression was also assessed in human colorectal carcinomas. Of the 28 Ahr^-/- mice, 10 developed cecal lesions by 50 weeks of age, an incidence significantly lower than previously reported. Cecal lesions of Ahr^-/- mice developed from serrated hyperplasia to adenoma/dysplasia-like neoplasia with enhanced proliferation. Macrophage and neutrophil infiltration into the lesions was also observed early in serrated hyperplasia, although adjacent mucosa was devoid of inflammation. Il1b, Il6, Ccl2, and Cxcl5 were up-regulated at lesion sites, whereas only IL-6 production increased in Ahr^-/- peritoneal macrophages after lipopolysaccharide + ATP stimulation. Neither Myc (alias c-myc) up-regulation nor β-catenin nuclear translocation was observed, unlike previously reported. Interestingly, enhanced phosphorylation of extracellular signal-regulated kinase, Src, and epidermal growth factor receptor and Amphiregulin up-regulation at Ahr^-/- lesion sites were detected. In human serrated lesions, however, AhR expression in epithelial cells was up-regulated despite morphologic similarity to Ahr^-/- cecal lesions. Our results suggest novel mechanisms underlying Ahr^-/- cecal tumorigenesis, depending primarily on cecum-specific mitogen-activated protein kinase pathway activation and inflammation.

A morphological and molecular study of proposed early forms of traditional serrated adenoma

AIMS

Traditional serrated adenoma (TSA) is the least common subtype of serrated colorectal polyp. Large protuberant lesions are easily recognised; however, the origins of TSAs are not known, and early forms have not been described. Some large TSAs present with a flat 'shoulder' component surrounding the central protuberant component. We hypothesised that small polyps with the same histology as these shoulder regions may represent early TSAs. Thus the primary aim of the study is to describe the histology of these presumptive early TSAs.

METHODS AND RESULTS

We collected 70 small (<10 mm) polyps that may represent early TSAs on the basis of typical TSA cytology covering the luminal surface. We also identified 12 large TSAs with a shoulder component resembling these small polyps. The study polyp patients had a mean age of 58 years, and 54% were female; the polyps had a mean diameter of 4.1 mm and were predominantly distal (71%). Morphologically, slit-like serrations were present in 81%, ectopic crypt formations were present in 67%, and a villous component was present in 47%. These histological features were similar to those of the 12 shoulder lesions. Immunohistochemical stains showed an absence of β-catenin nuclear expression in 96% of the small polyps, retained expression of MLH1 in 100%, and Ki67 positivity restricted to the crypt bases and ectopic crypt formations. BRAF and KRAS mutations were identified in 47% and 31% of the polyps, respectively. BRAF-mutated polyps were more likely than KRAS-mutated polyps to arise in a precursor polyp (82% versus 18%, P < 0.001), and were more likely to have slit-like serrations (100% versus 73%, P = 0.003).

CONCLUSIONS

These morphological, immunohistochemical and molecular findings are similar to what has been reported in large TSAs, and support the hypothesis that these polyps represent early forms of TSA.

BCL2 Expression and its Correlation with Neuroendocrine Differentiation in Colon Carcinomas

Aims and background

In this study we investigated the association between BCL2 expression and neuroendocrine differentiation in tubular adenomas and colon carcinomas. We also evaluated the prognostic significance of BCL2 expression and neuroendocrine differentiation in the carcinoma group.

Methods

Forty-eight colon carcinomas and twelve tubular adenomas were stained immunohistochemically with BCL2 and chromogranin A (CgA). Staining patterns were scored semiquantitatively and correlated with tumor type, tumor grade, Dukes stage, and survival time.

Results

BCL2 expression was detected in 7 of 12 (58.3%) adenomas and 37 of 48 (77.0%) carcinomas. In normal mucosa we observed positive staining only in the basal portions of the crypts. However, diffuse positivity was observed in the adenomas and carcinomas. Carcinomas had significantly higher BCL2 scores than the normal group, but we did not observe any significant differences either between the adenoma and carcinoma group or between the adenoma and normal group. BCL2 scores were higher in stage B than in stage C tumors, and in adenocarcinomas than in mucinous carcinomas. CgA positivity was observed in 24 of 48 (50%) carcinomas. It was not detected in adenomas. We did not find a significant correlation between CgA expression and any of the clinicopathological parameters.

Conclusion

On consecutive sections BCL2 and CgA positivity closely paralleled each other and a significant positive correlation was observed between CgA and BCL2 expression. These findings suggest a close association between BCL2 expression and neuroendocrine differentiation and indicate that BCL2 may be involved in neuroendocrine differentiation in addition to its role in protecting cells from apoptosis.

Traditional serrated adenoma of the colorectum: clinicopathologic implications and endoscopic findings of the precursor lesions

OBJECTIVES

To investigate the clinicopathologic and endoscopic features of precursor lesions associated with traditional serrated adenomas (TSAs).

METHODS

Mutation studies for BRAF, KRAS, PIK3CA, and EGFR and immunohistochemical staining for Ki-67 were performed on 107 TSAs from 104 patients.

RESULTS

Nondysplastic hyperplastic polyp (HP) or sessile serrated adenoma/polyp (SSA/P) precursor lesions were found in 56 (52.3%) TSAs, among which 32 (57.1%) cases showed a flat-elevated lesion with a type II pit pattern during endoscopy. TSAs with an SSA/P precursor lesion were usually found in the proximal colon, while TSAs with an HP or with no precursor lesion were mainly located in the distal colon and rectum (P < .001). TSAs with a precursor lesion showed a lower frequency of conventional epithelial dysplasia and KRAS mutation as well as a higher frequency of BRAF mutation compared with those with no precursor lesion (P = .002, P < .001, and P < .001, respectively).

CONCLUSIONS

A significant proportion of HP or SSA/P precursor lesions accompanied by TSAs can be detected by endoscopy based on both their flat-elevated growth and type II pit patterns. The heterogeneity of TSAs in terms of clinicopathologic and molecular features correlated with the status or type of precursor lesions.

Development of Cryptosporidium parvum-induced gastrointestinal neoplasia in severe combined immunodeficiency (SCID) mice: severity of lesions is correlated with infection intensity

We reported previously that Cryptosporidium parvum was able to induce intestinal tumors in severe combined immunodeficiency (SCID) mice treated with corticoids. To further characterize this Cryptosporidium-induced cell transformation, SCID mice treated with dexamethasone were challenged with C. parvum oocysts, and euthanatized sequentially after infection for histologic examination. Ki-67 was used as a marker of cellular proliferation. Our previous results were confirmed, and it was also found that mice receiving higher inocula (10(6)-10(7)) experienced more severe neoplastic development. Additionally, neoplastic changes were observed not only in the caecum but also in the stomach and duodenum of some animals. Interestingly, SCID mice (6/6) inoculated with 10(5)-10(7) oocysts showed high grade intraepithelial neoplasia or adenomas with high grade dysplasia in the caecum after Day 46 post-infection (PI). Immunohistochemistry for Ki-67 staining indicated the neoplastic process associated to cryptosporidiosis, and evidenced the first immunohistochemical alterations at early stages of the process, even at 3 weeks PI.

Differential rates of proliferation and apoptosis in nasal polyps correspond to alterations in DNA spatial distribution and nuclear polarization as observed by confocal microscopy

The study aimed to investigate the expression of p53, Bcl-2 and Ki-67 in relation to the histologic and nuclear qualitative and spatial characteristics of chronic rhinosinusitis with polyposis (CRP). Imprint smears obtained from surgically removed nasal polyps of 20 patients were studied. The polyps were classified according to their histological characteristics as: hyperplasia (simple and pronounced) and squamous metaplasia. The expression of p53, Bcl-2 and Ki-67 was assessed by immunocytochemistry. DNA spatial distribution and nuclear orientation were studied by staining with propidium iodide and examined by confocal microscopy. Positive immunoreaction for p53, Ki-67 and Bcl-2 was observed in 50, 65, and 50% of polyp's smears, respectively. For each diagnosis, the rates were simple hyperplasia 60, 80 and 30%, pronounced hyperplasia 80, 100 and 40%, metaplasia 0, 0 and 100%, respectively. Abnormal chromatin distribution and nuclear disorientation was observed in three cases of pronounced hyperplasia combined with positive immunoreaction for Ki-67 and p53 and negative immunoreaction for Bcl-2. CRP demonstrated different proliferation and apoptotic rates, according to their histology. Nuclear characteristics observed by confocal microscopy are associated with the immunocytochemical markers of proliferation and apoptosis.

Pathologic features and biologic importance of colorectal serrated polyps

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

Gene profiling of colonic serrated adenomas by using oligonucleotide microarray

PURPOSE

The serrated pathway has been proposed as an important concept explaining the colorectal carcinogenesis. However, the key molecules of the serrated pathway which contribute to the formation of serrated polyp are still poorly understood. To elucidate the molecular genetic basis of the serrated pathway, we performed an initial oligonucleotide microarray to analyze the gene expression pattern of patients with colonic serrated adenomas.

METHODS

Oligonucleotide microarrays containing 3,096 genes were used to compare individual gene profiles of serrated adenoma samples (n = 5) and normal mucosal samples obtained from colon in patients by colonoscopy. Three genes were further investigated by means of quantitative reverse transcription polymerase chain reaction (RT-PCR) for validation. The Significance Analysis of Microarray (SAM) package method was used to identify differentially expressed genes.

RESULTS

Compared with normal colonic mucosa tissue, 73 genes were upregulated at least twofold, and 51 genes were downregulated by at least 50% in serrated polyp samples (approximately 3.6% of genes evaluated) with a p-value of less than 0.05. Moreover, some of the gene expression patterns observed were similar to those of previously reported in colorectal cancer, suggesting reinforcement of tendency to malignancy. Three genes (TNFRSF10A, BENE, RARA) with strongly significant expression intensities in the oligonucleotide microarray results were validated by quantitative RT-PCR. TNFRSF10A had upregulated expression patterns while BENE, RARA had downregulated expression pattern.

CONCLUSION

Although our report presents only preliminary results, we think they provide important data regarding serrated adenomas not only to better define the precise mechanism of genetic changes involved as the main member in serrated pathway of colorectal carcinogenesis but also to yield practical information for identifying optimized diagnostic modalities.

Sessile serrated adenoma (SSA) vs. traditional serrated adenoma (TSA)

The morphologic distinction between various serrated polyps of the colorectum may be challenging. The distinction between sessile serrated adenoma (SSA) and traditional serrated adenoma (TSA) may be difficult using currently available criteria mostly based on cytologic characteristics. We have evaluated 66 serrated polyps including 29 SSA, 18 TSA, and 19 hyperplastic polyps for overall shape of the polyps, architectural features of individual crypts, the presence of eosinophilic cytoplasm, size and distribution of the proliferation and maturation zones, as well as Ki-67 and CK20 expression. The extent of the expression of CK20 and Ki-67 could not distinguish between the 3 types of serrated polyps, but the distribution of their expression was very helpful and differences were statistically significant. The distribution of Ki-67+ cells was the single most helpful distinguishing feature of the serrated polyp type (P<0.0001, chi test). Hyperplastic polyps had regular, symmetric, and increased Ki-67 expression. SSA had irregular, asymmetric, and highly variable expression of Ki-67. TSA had low Ki-67 expression, which was limited to "ectopic crypts" and admixed tubular adenomalike areas. In serrated polyps, ectopic crypt formation (ECF) defined by the presence of ectopic crypts with their bases not seated adjacent to the muscularis mucosae was nearly exclusive to TSA and was found in all cases, while the presence of cytologic atypia and eosinophilia of the cytoplasm were characteristic, but not limited to TSA. No evidence of ECF, but nevertheless abnormal distribution of proliferation zone was characteristic of SSA, whereas HP had neither. The presence of the ECF defines TSA in a more rigorous fashion than previous diagnostic criteria and also explains the biologic basis of exuberant protuberant growth associated with TSA and the lack of such growth in SSA. Recognition of this phenomenon may also help in exploring the genetic and molecular basis for differences between SSA and TSA, because these architectural abnormalities may well be a reflection of abnormalities in genetically programmed mucosal development.

Utility of MIB-1 (Ki-67) in Evaluating Diminutive Colorectal Polyps With Cautery Artifact

Context.—Accurate interpretation of colorectal polyp histology is essential in the decision-making process during treatment and surveillance following polypectomies. However, interpretation of diminutive colorectal polyps removed by thermal electrocoagulation (hot biopsy technique) is often problematic as a result of cautery artifact.

Objective.—To evaluated the usefulness of the proliferation marker MIB-1 (Ki-67) as an aid in the differential diagnosis of diminutive colorectal polyps with cautery artifact, as adenomatous and nonadenomatous polyps display different patterns of epithelial proliferation.

Design.—Seventy-five diminutive colorectal polyps with extensive cautery artifact displaying at least the upper portions of 3 adjacent crypts with the corresponding surface epithelium were evaluated and immunolabeled with MIB-1. They included 25 cases in which a definitive or presumptive diagnosis could not be reached (indeterminate polyps), 25 cases diagnosed as compatible with adenomatous polyp, and 25 cases diagnosed as compatible with nonadenomatous polyp.

Results.—MIB-1 immunoreactivity was well preserved in the cauterized areas. Among indeterminate polyps, MIB-1 stained upper crypts and surface epithelium in 14 cases (adenomatous polyp staining pattern) and revealed minimal or absent staining in these areas in 11 cases (nonadenomatous polyp staining pattern). All cases diagnosed as compatible with adenomatous polyp displayed the adenomatous polyp staining pattern. In contrast, all cases diagnosed as compatible with nonadenomatous polyp revealed the nonadenomatous polyp staining pattern.

Conclusions.—Immunoreactivity for MIB-1 may be used as a beneficial adjunctive test to help diagnose diminutive colorectal polyps with extensive cautery artifact.

Clinico-pathological aspects of colorectal serrated adenomas

AIM: To study the association of colorectal serrated adenomas (SAs) with invasive carcinoma, local recurrence, synchronicity and metachronicity of lesions.

METHODS: A total of 4536 polyps from 1096 patients over an eight-year period (1987-1995) were retrospectively examined. Adenomas showing at least 50% of serrated architecture were called SAs by three reviewing pathologists.

RESULTS: Ninety-one (2%) of all polyps were called SAs, which were found in 46 patients. Invasive carcinomas were seen in 3 out of 46 (6.4%) patients, of whom one was a case of familial adenomatous polyposis (FAP). A male preponderance was noted and features of a mild degree of dysplasia were seen in majority (n=75, 83%) of serrated adenomas. Follow-up ranged 1-12 years with a mean time of 5.75 years. Recurrences of SAs were seen in 3 (6.4%) cases, synchronous SAs in 16 (34.8%) cases and metachronous SAs in 9 (19.6%) cases.

CONCLUSION: Invasive carcinoma arising in serrated adenoma is rare, accounting for 2 (4.3%) cases studied in this series.

Serrated adenoma of the colorectum and the DNA-methylator phenotype

Serrated adenomas (SA) of the colorectum show features intermediate between hyperplastic polyps (HP) and adenomas. HP and SA are related lesions and there is now strong evidence for a 'serrated-polyp pathway' to colorectal cancer (CRC) that is largely independent of the classic adenoma-to-carcinoma sequence. A recently recognized lesion in this pathway is a HP variant characterized by relatively large size, atypical histology and proximal location in the colorectum. This HP variant has been given a variety of names in the literature including 'sessile SA' and 'type I SA'. Because this lesion lacks the traditional cytology of colorectal adenoma and in order to avoid confusion with SA, it is referred to in this review as sessile serrated polyp. SA are characterized by a heterogeneous group of changes at the molecular level, but a high proportion have BRAFmutations and DNA methylation. They may develop in HP or sessile serrated polyps, or may arise de novo. In the serratedpolyp pathway, the advent of genetic instability is likely to be an important rate-limiting step that drives rapid neoplastic evolution. Methylation and inactivation of the DNA repair genes MLH1 and MGMT (O-6-methylguanine-DNA methyltransferase) have been proposed as critical steps leading to genetic instability. Stretches of DNA rich in the bases guanine and cytosine (CpG islands; where p represents a phosphodiester bond linking adjacent cytosine and guanine bases) that are normally unmethylated may become methylated in malignant human colorectal tumors. Subsets of colorectal cancers with an unusually high number of methylated CpG islands have been described as having the 'CpG-island-methylator phenotype' It is possible that many, if not all, CRCs with the CpG-island-methylator phenotype evolve through the serrated-polyp pathway that would, therefore, explain approximately 20% of all CRCs. The current lack of guidelines for managing serrated polyps may explain the static incidence of proximal CRC, despite the falling incidence rates for left-sided CRC during the same time period.

Differential labeling by monoclonal antibodies Adnab-9 and anti-alpha-defensin 5 based on the distribution and adenomatous tissue content of colonic polyps

We sought a correlation between site and morphology of colonic polyps by labeling with neoplastic and general Paneth cell markers, monoclonal antibodies Adnab-9 and anti-alpha-defensin 5, respectively. Proportions labeled by Adnab-9 and anti-alpha-defensin 5 were, respectively, 42 and 85% for adenomas, 39 and 63% for early tubular adenomas, 41 and 44% for serrated, 34 and 20% for mixed, and 11 versus 2.7% for hyperplastic polyps. Compared with hyperplastic polyps, the proportion of other polyps labeled by Adnab-9 or anti-alpha-defensin 5 was higher but this difference was more significant for distal (P = 0.008 for Adnab-9 and P = 0.0001 for anti-alpha-defensin 5) than proximal (P = 0.645 and P = 0.154, respectively) polyps. While increased labeling of all proximal polyps compared to distal ones mirrored the colonic distribution of Paneth cells, distal adenomas tended to have a higher proportion labeled by Adnab-9, suggesting that Adnab-9 labels Paneth cells associated with increased neoplastic potential.

Cell turnover of serrated adenomas

Serrated adenomas of the colon are characterized by epithelial neoplasia combining the architectural features of hyperplastic polyps and the cytological features of adenomas. Cell turnover, which is related to the malignant potential of these polyps, has not been thoroughly investigated. The aim of this study was to investigate epithelial cell proliferation, apoptosis, and oncoprotein expression in serrated adenomas. Twenty-five hyperplastic polyps, 25 serrated adenomas, and 25 tubulovillous adenomas resected from the colons of 75 patients were studied by immunohistochemical staining using monoclonal antibodies against MIB-1, Bcl-2, Bax, p53, and the TUNEL method for the detection of apoptosis. In serrated adenomas, the proliferation rate was significantly lower than in tubulovillous adenomas in both the lower and the upper parts of the crypts, and higher than that of hyperplastic polyps. Apoptosis was also significantly lower in serrated than in tubulovillous adenomas, but higher than in hyperplastic polyps. p53 oncoprotein expression was significantly greater in both serrated and tubulovillous adenomas than in hyperplastic polyps. bcl-2 protein expression was higher only in tubulovillous adenomas. Bax index was significantly different between tubullovillous and serrated adenomas, but the lowest values were observed in hyperplastic polyps. Serrated adenomas are highly proliferative polyps. They should be considered a biologically different entity from hyperplastic polyps. The intermediate features between serrated adenomas, hyperplastic polyps, and tubulovillous adenomas using the antibodies analysed in this study could have implications for the rate or the mechanism of development of malignancy in this type of polyp.

Molecular differences between sporadic serrated and conventional colorectal adenomas

PURPOSE

The purpose is to compare the molecular characteristics of serrated adenomas (SAs) with those of conventional adenomas (CADs) and hyperplastic polyps (HPs).

EXPERIMENTAL DESIGN

We evaluated the proliferative activity and molecular alterations in 47 SAs (25 pure-type and 22 mixed-type), 71 CADs, and 23 HPs.

RESULTS

The proliferative activity of SAs, as evaluated by Ki-67 expression, was intermediate between CADs and HPs. There was no significant difference in the incidence of KRAS or p53 mutations between the three histological groups. In the microsatellite instability (MSI) analysis, 21% of SAs (9 of 43) showed MSI at two or more loci (MSI-H); corresponding values were 5% of CADs (3 of 64) and 8% of HPs (1 of 13; SAs versus CADs, P = 0.0125). MSI-H was more likely to be found in pure-type SAs (36%; 8 of 22) than in mixed-type SAs (5%; 1 of 21; P = 0.0212). Loss of hMLH-1 expression was found in 8 of 9 SAs with MSI-H. The incidence of BRAF or KRAS mutations was 36 and 15% of SAs, respectively; the combined incidence of BRAF and KRAS mutations occurred in 49% of SAs. However, there was no significant difference in the incidence of BRAF or KRAS mutations between SAs with and without MSI-H.

CONCLUSIONS

Genetic instability is more frequently implicated in the tumorigenesis of SAs, especially pure-type SAs, than in that of CADs. In contrast, activation of the Ras/Raf/MEK/MAP kinase cascade by BRAF or KRAS mutation, independently of the genetic instability, may be associated with the progression of about half of SAs.

Small early tubular adenomas and mixed colonic polyps found on screening flexible sigmoidoscopy do not predict proximal neoplasia in males

BACKGROUND & AIMS

Distal colonic adenomas found on flexible sigmoidoscopy are associated with proximal neoplasias, thus requiring a complete colonoscopic examination, but data regarding the association of distal mixed polyps with proximal neoplasia are lacking. We conducted this study to elucidate the significance of distal mixed colonic polyps in predicting proximal neoplasia.

METHODS

We retrospectively analyzed data from patients who underwent a flexible sigmoidoscopic examination for colorectal cancer screening and a follow-up colonoscopic examination because of distal colonic polyps. Distal index polyps were classified by a pathologist as early tubular adenoma (ETA), serrated, or true mixed categories. Index polyps also were immunostained with a monoclonal antibody, Adnab-9, a marker for the colorectal adenoma carcinoma sequence.

RESULTS

In 636 patients with distal index polyps, 6% were malignant, 55% were adenomas, 13% were ETAs, 6% were serrated, 4% were true mixed, and 17% were hyperplastic. Compared with distal hyperplastic index polyps, distal malignant polyps (P = 0.0006) and adenomas (P = 0.001) were associated with a significantly increased number of synchronous proximal neoplasia, but the small distal mixed, serrated, or ETA did not predict the increased incidence of proximal neoplasia. Large distal polyps of each category were significantly associated with an increased number of synchronous proximal neoplasias. In support of these findings, immunostaining of distal polyps with Adnab-9 showed predictability for proximal neoplasia only in the adenoma category (P < 0.05).

CONCLUSIONS

Small ETAs, serrated, or mixed polyps found on flexible sigmoidoscopic examination do not increase the probability of synchronous proximal neoplasia.

Clinicopathologic and endoscopic features of colorectal serrated adenoma: differences between polypoid and superficial types

BACKGROUND

Serrated adenoma is a distinct histologic colorectal lesion. There are two macroscopic types: polypoid and superficial. The aim of this study was to clarify clinicopathologic and endoscopic differences between polypoid and superficial serrated adenomas.

METHODS

An analysis was conducted of the clinicopathologic and endoscopic features for 240 polypoid and 127 superficial serrated adenomas examined by colonoscopy, and the surface pit patterns of 114 polypoid and 64 superficial serrated adenomas examined by magnifying videoendoscopy.

RESULTS

The male:female gender ratio for the polypoid serrated adenomas (3.5:1) was significantly higher than that for the superficial serrated adenomas (1.7:1). Superficial serrated adenomas were significantly larger than polypoid serrated adenomas (mean [standard deviation], respectively, 10.1 [7.9] mm vs. 6.3 [4.6] mm). In the distal segments of the colorectum, polypoid serrated adenomas were more common than superficial serrated adenomas. Granulonodular and lobular appearances at endoscopy were significantly more common for polypoid (23.3%) than for superficial serrated adenomas (7.1%). Pit patterns differed between the lesion types: polypoid serrated adenomas had type III(L) or IV pit patterns; all superficial serrated adenomas had the type II pit pattern. The relative frequency of occurrence of high-grade dysplasia and carcinoma in situ among superficial serrated adenomas (25.2%) was significantly greater than that among polypoid serrated adenomas (9.2%). The tubulovillous growth pattern was significantly more common in polypoid tumors (31.5%) than in superficial tumors (0%).

CONCLUSIONS

Polypoid and superficial serrated adenomas have different clinicopathologic characteristics and growth patterns.

Proliferation kinetics and apoptosis of serrated adenoma of the colorectum

To elucidate the proliferation kinetics and cell loss by apoptosis of serrated adenoma (SA) of the colorectum, we performed Ki-67 immunohistochemistry and the terminal deoxynucleotidyl transferase (TdT)-mediated biotinylated deoxyuridine-triphosphate nick-end labeling (TUNEL) method for 24 SA, and compared the results to those of normal colonic mucosa (n = 15), hyperplastic polyp (HP) (n = 18) and traditional tubular adenoma (TA) (n = 55). The growth fraction (Ki-67 labeling index) of SA was 18.8%, which was significantly lower than those of TA (40.1%) and HP (23.8%), while the apoptotic index of SA (0.14%) was significantly lower than that of TA (1.17%). The proliferative compartment in SA was distributed either basally (47%, 60/117 crypts), or in the intermediate portion (51.3%, 55/117 crypts), and there was no superficial translocation of the proliferative compartment, which was seen in 81.2% (361/445 crypts) of TA crypts. These results indicate that SA is a tumor with low proliferative activity and its growth would be maintained by a low extent of cell loss by apoptosis. The results also indicate the neoplastic process in SA is characterized by the disorder of cell migration, maturation and exfoliation similar to HP, and its epithelial cell maturation and migration occasionally occur bidirectionally, toward the surface and to the bottom of the crypt.

Cellular differentiation status of epithelial polyps of the colorectum: the gastric foveolar cell-type in hyperplastic polyps

AIMS

The 'metaplastic' polyp of the colorectum, a synonym for the hyperplastic polyp, was named based only on features of the crypt epithelium. It is considered non-neoplastic, but the precise cellular differentiation status remains to be proven.

METHODS AND RESULTS

Forty-eight hyperplastic polyps, 12 serrated adenomas, 45 tubular adenomas and five juvenile polyps were studied for their phenotypic expression using gastric (foveolar or pyloric gland cell), small intestinal (goblet cell), and colonic (goblet cell) cellular markers by immunohistochemical and mucin histochemical techniques. Gastric foveolar cell-type differentiation was significantly expressed in hyperplastic polyps, while colonic differentiation was also consistently preserved. Neither gastric pyloric-type nor small intestinal differentiation was observed. The same cell differentiation status as hyperplastic polyps was observed in serrated adenomas but not in tubular adenomas or juvenile polyps.

CONCLUSIONS

A large proportion of hyperplastic polyps are composed of hybrid epithelium, with bidirectional differentiation to both gastric foveolar and colonic epithelial cells in the same crypt. Therefore hyperplastic polyps might be interpreted as the outcome of abnormal cell differentiation of stem cells. The same phenotypic expression suggests that hyperplastic polyps and serrated adenomas share the same cell lineage.

Frequent CpG island methylation in serrated adenomas of the colorectum

Serrated adenomas are characterized by a saw-toothed growth pattern with epithelial dysplasia (intraepithelial neoplasia). The CpG island methylator phenotype (CIMP) is a recently described mechanism for tumorigenesis in colorectal carcinomas and adenomas characterized by methylation of multiple CpG islands. The role of these epigenetic alterations in the pathogenesis of serrated adenomas is not clear. We therefore evaluated CIMP in 22 sporadic serrated adenomas and 6 serrated adenomas with multiple (6 to 10) hyperplastic polyps, including 5 with admixed hyperplastic glands and adenomatous glands, and compared the results with 34 conventional adenomas. Bisulfite methylation-specific polymerase chain reaction was used for the p16 and hMLH1 genes, and three MINT (methylated in tumor) loci (MINT1, MINT2, and MINT31). Patients with sporadic serrated adenomas had a higher frequency of hyperplastic polyps (1.3 +/- 1.6) as compared to patients with tubular adenomas (0.4 +/- 0.9, P = 0.02). Mean number of methylated sites was significantly higher in sporadic serrated adenomas (2.0 +/- 1.7) than in tubular adenomas (0.8 +/- 0.9, P = 0.00001). Sporadic serrated adenomas had significantly more frequent methylation of MINT1 (48%, 10 of 22) and MINT2 (71%, 15 of 21) than tubular adenomas (9%, 3 of 34, P = 0.001; and 18%, 6 of 34, P = 0.0001), respectively. Concordant methylation of two or more sites (CIMP-high) was also more frequent in sporadic serrated adenomas (68%, 15 of 22) than in tubular adenomas (18%, 6 of 34, P = 0.0005). All five serrated adenomas with admixed hyperplastic glands and adenomatous glands were CIMP-high. Our results indicate that CpG island methylation is common in sporadic serrated adenomas and may play an important role in their pathogenesis.

Expression of Ki-67 and cytokeratin 20 in hyperplastic polyps of the colorectum

AIMS

To study the expression of Ki-67 and cytokeratin 20 (CK20) in a group of hyperplastic polyps (including a group with "atypical" features) with the aim of determining whether upper crypt Ki-67 staining and lower crypt CK20 staining correlated with these atypical features, as assessed by light microscopy.

METHODS

Fifty seven formalin fixed, paraffin wax embedded hyperplastic colorectal polyps from 53 patients were selected on histological grounds; these comprised 26 typical polyps and 31 with atypical features, which included nuclear hyperchromatism, basal crowding, and increased mitotic activity. These polyps were examined using a standard immunohistochemical method with antibodies against CK20 and Ki-67. Comparisons were made with normal mucosa, adenomatous polyps, and carcinomas.

RESULTS

Of the 26 typical polyps, 17 showed the usual pattern of lower crypt Ki-67 and upper crypt CK20 staining; one with upper crypt Ki-67 staining but normal surface CK20 staining; seven with Ki-67 confined to the lower half of crypts but with scattered lower crypt CK20; and one with both upper crypt Ki-67 staining, together with scattered CK20 basal staining. Of the 31 polyps with atypical features, 11 showed the usual staining pattern of lower crypt Ki-67 staining and surface staining with CK20; two showed Ki-67 staining extending into the upper half of crypts, but with a normal surface staining with CK20; 14 showed Ki-67 confined to the lower half of crypts, but scattered lower crypt staining with CK20; and four showed upper crypt Ki-67 staining together with scattered CK20 lower crypt staining.

CONCLUSIONS

The normal pattern of lower crypt Ki-67 and upper crypt CK20 was seen in 28 of the 57 hyperplastic polyps and, in general, this corresponded with standard light microscopic appearances. Twenty one of the 57 polyps showed lower crypt mosaic CK20 staining, which in general corresponded with basal abnormalities on light microscopy, although seven specimens had normal appearances. Two smaller subsets emerged, one showing upper crypt Ki-67 staining in the presence of normal CK20 expression (three cases) and another in which a combination of lower crypt CK20 and upper crypt Ki-67 expression was seen (five cases). This last pattern was similar to that of neoplastic polyps and raises the possibility that a subgroup of hyperplastic polyps exists that may be a variant with malignant potential. Further studies with markers of mismatch repair genes and K-ras mutations may help to clarify this issue.

Emerging concepts in colorectal neoplasia

An understanding of the mechanisms that explain the initiation and early evolution of colorectal cancer should facilitate the development of new approaches to effective prevention and intervention. This review highlights deficiencies in the current model for colorectal neoplasia in which APC mutation is placed at the point of initiation. Other genes implicated in the regulation of apoptosis and DNA repair may underlie the early development of colorectal cancer. Inactivation of these genes may occur not by mutation or loss but through silencing mediated by methylation of the gene's promoter region. hMLH1 and MGMT are examples of DNA repair genes that are silenced by methylation. Loss of expression of hMLH1 and MGMT protein has been demonstrated immunohistochemically in serrated polyps. Multiple lines of evidence point to a "serrated" pathway of neoplasia that is driven by inhibition of apoptosis and the subsequent inactivation of DNA repair genes by promoter methylation. The earliest lesions in this pathway are aberrant crypt foci (ACF). These may develop into hyperplastic polyps or transform while still of microscopic size into admixed polyps, serrated adenomas, or traditional adenomas. Cancers developing from these lesions may show high- or low-level microsatellite instability (MSI-H and MSI-L, respectively) or may be microsatellite stable (MSS). The suggested clinical model for this alternative pathway is the condition hyperplastic polyposis. If colorectal cancer is a heterogeneous disease comprising discrete subsets that evolve through different pathways, it is evident that these subsets will need to be studied individually in the future.

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

OBJECTIVES

There is growing interest in the biological and molecular features and neoplastic potential of colonic hyperplastic polyps because of the recent finding of K-ras mutations in many of these lesions. Hyperplastic polyps may also develop in chronic ulcerative colitis (CUC), but it is unclear if these are biologically similar to the sporadic type. The aim of this study was to evaluate and compare the molecular profile of CUC-associated hyperplastic polyps with sporadic hyperplastic polyps of the colon.

METHODS

Thirty-nine hyperplastic polyps from 26 CUC patients, 39 sporadic hyperplastic polyps from 29 age- and sex-matched patients without CUC, and 26 colonic mucosal biopsies from 22 patients with CUC but without hyperplastic polyps were analyzed by polymerase chain reaction for loss of heterozygosity of APC, 3p, p53, and p16 and for mutations in codons 12, 13, and 61 of the K-ras gene. Immunohistochemical evaluations for the proliferation-associated nuclear peptide Ki67 (MIB-1) and p27 were also performed on a subset of hyperplastic polyps.

RESULTS

CUC-associated hyperplastic polyps showed a proportion of genetic alterations (47%) similar to that of sporadic hyperplastic polyps (33%) (p > 0.05), and neither significantly differed from chronically inflamed mucosae in CUC patients without hyperplastic polyps. Furthermore, in a small group of CUC patients in which informative tissue was available from both their hyperplastic polyps and adjacent flat colitic mucosae, the polyps contained mutations that were not present in the underlying mucosa. Loss of heterozygosity of APC, 3p, p53, p16, and K-ras mutations were present in 21%, 40%, 27%, 20%, and 19% of CUC patients with hyperplastic polyps, respectively, and in 0%, 11%, 20%, 13%, and 13% of non-CUC patients with sporadic polyps, respectively. Both CUC-associated and sporadic hyperplastic polyps showed a substantial number of cases (46% and 64% of cases, respectively) with loss of p27 expression, and both types of lesions showed similar MIB-1 proliferation indices.

CONCLUSIONS

These data suggest that CUC-associated hyperplastic polyps are genotypically similar to the sporadic type. This study adds to the expanding list of molecular alterations that have been discovered in hyperplastic polyps, and lends further support to the controversial theory that these lesions may have neoplastic potential.

Three-dimensional reconstruction and fractal geometric analysis of serrated adenoma

Serrated adenoma (SA) is a relatively newly defined entity of colorectal neoplasm first characterized by Longacre and Fenoglio-Preiser in 1990. This lesion is characterized by a complicated serrated edge of crypts. In this study, we performed three-dimensional (3-D) reconstruction, including 3-D distribution patterns of Ki-67-positive cells and fractal dimension of SA, in order to evaluate the nature of the complicated architecture, including its possible morphogenesis. We studied nine colonoscopic polypectomy specimens including three SAs, three tubular adenomas (TAs), and three hyperplastic polyps (HPs). Sixty serial tissue sections per case were stained alternately with hematoxylin and eosin (H&E) and Ki-67 immunostain. Each serial image was then digitized for 3-D computer analysis and the distribution pattern of Ki-67-positive cells was evaluated. Ki-67-immunostained sections were also subjected to 2-D quantitative morphometric study. In addition, the fractal dimensions of images from H&E-stained sections were examined using a box-counting method. Results of the 3-D reconstruction study demonstrated that glandular budding and branching were more frequent in SA than in TA or HP. These findings were confirmed quantitatively by the results of fractal geometric analysis of these polyps (fractal dimension:1.34 +/- 0.08 for SA, 1.23 +/- 0.07 for TA, and 1.28 +/- 0.12 for HP). Ki-67-positive cells in HP were localized mainly in the bottom of crypts and those in TA were diffusely distributed, while Ki-67-positive cells in SA were mainly aggregated in the depressed sites of serrated epithelia. These findings were also confirmed quantitatively using 2-D morphometry. These distribution patterns of the proliferative zone of SA are considered to contribute to the formation of the characteristic serrated epithelia and the complicated morphological appearance of SA.

Apoptosis index and apoptosis-related antigen expression in serrated adenoma of the colorectum: the saw-toothed structure may be related to inhibition of apoptosis

Serrated adenoma of the colorectum is a recently proposed entity characterized by a saw-toothed structure of hyperplastic polyp and cytologic atypia of tubular adenoma. To clarify the role of apoptosis in morphogenesis of serrated adenoma, we investigated apoptotic indices and expression of apoptosis-related antigens in the tumor cells. Thirty-eight serrated adenomas were examined by the nick-end DNA labeling method and immunostained for CD95 (Fas), bcl-2, bax, and p53. Thirty-seven hyperplastic polyps, 48 tubular adenomas, and 16 sections containing normal colonic mucosa were similarly examined for comparison. The apoptotic indices in the upper and middle zones of the crypts of serrated adenomas and hyperplastic polyps were lower than those of normal colon mucosa and tubular adenomas with statistically significant differences. The CD95 expression was diffusely observed throughout the epithelium of normal crypts and tubular adenomas, whereas it was reduced in serrated adenomas and hyperplastic polyps. The bcl-2 expression was confined to the basal crypts in the latter two lesions but was diffuse throughout the neoplastic epithelium in tubular adenomas. The bax expression was increased in serrated adenomas and tubular adenomas but was decreased in hyperplastic polyps. Overexpression of p53 protein was observed in 50% of serrated adenomas, none of hyperplastic polyps, and 14% of tubular adenomas. These findings suggest that inhibition of apoptosis is caused by reduced CD95 expression in serrated adenomas and hyperplastic polyps, which may induce the characteristic saw-toothed structure in these lesions. Based on the similarities and differences between serrated adenoma and hyperplastic polyp observed in the present study, a progression from the latter to the former lesion may be postulated.

Evolution of colorectal cancer: change of pace and change of direction

This review compiles evidence for an alternative to the classical adenoma-carcinoma sequence in the evolution of colorectal cancer. It is suggested that between 30 and 50 of colorectal cancers are not initiated by mutation of the tumor suppressor gene APC, but through the epigenetic silencing of genes implicated in the control of differentiation, cell cycle control and DNA repair proficiency. The precursor polyps are often characterized by a serrated architecture, and include hyperplastic polyps, admixed polyps and serrated adenomas. The alternative pathway is heterogeneous and may culminate in cancers showing low or high level DNA microsatellite instability (MSI-L and MSI-H, respectively), and in cancers that are microsatellite stable (MSS). Cancers showing DNA MSI may be characterized by an accelerated evolution. Cancers in hereditary non-polyposis colorectal cancer show features of both classical (adenoma and APC mutation) and alternative pathways (rapid evolution, MSI-H and lack of chromosomal instability).

Cyclooxygenase-2 is overexpressed in serrated adenoma of the colorectum

PURPOSE

The aim of this study was to clarify whether cyclooxygenase-2 and cyclooxygenase-1 is expressed in hyperplastic polyps and serrated adenomas.

METHODS

Forty-nine serrated adenomas and 25 hyperplastic polyps were immunostained using anticyclooxygenase-2 and anticyclooxygenase-1 antibodies. Cyclooxygenase-2 and cyclooxygenase-1 expression was investigated in all specimens.

RESULTS

Cyclooxygenase-2 was expressed in dysplastic glands in the majority of serrated adenomas. Thirty-five of 49 (71.4 percent) serrated adenomas exhibited moderate to intense cyclooxygenase-2 immunoreactivity, and 8 of 25 hyperplastic polyps (32 percent) showed weak to moderate cyclooxygenase-2 immunoreactivity. Cyclooxygenase-1 immunoreactivity was very weak in all the hyperplastic polyps and serrated adenomas.

CONCLUSIONS

These results suggest that cyclooxygenase-2 is overexpressed in serrated adenoma of the colorectum. Cyclooxygenase-2 inhibitors will reduce the incidence of serrated adenomas.

Colonic intra-epithelial carcinoma occurring in a hyperplastic polyp via a serrated adenoma

We present a case of intra-epithelial carcinoma occurring in a serrated adenoma of the colon. The pedunculated polyp, which measured 12 x 10 x 6 mm, was endoscopically removed from the ascending colon of a 78-year-old woman. Histologically, the polyp mainly consisted of serrated adenomatous glands, and had foci of intra-epithelial carcinoma at the top. Hyperplastic (metaplastic) areas were also present in both borders between the serrated adenomatous area and the surrounding normal mucosa. A sequential increase in the degree of dysplasia, and in the number of nuclei positively reactive for Ki-67 and p53 was evident from the hyperplastic areas toward the foci of carcinoma. The polyp described here may represent a carcinogenic potential of hyperplastic polyp via serrated adenoma.

Expression of survivin in normal, hyperplastic, and neoplastic colonic mucosa

The regulation of apoptotic cell death may have a profound effect on the pathogenesis and progression of colon cancer. Survivin, a member of the inhibitor of apoptosis gene family, has been detected in fetal tissue and in a variety of human malignancies. In the current study, we investigated survivin expression by an immunohistochemical approach in benign, hyperplastic, premalignant, and malignant lesions of the colon. Survivin was detected in all cases of normal colonic mucosa (20/20), hyperplastic polyps (20/20), adenomatous polyps (20/20), and in both well differentiated and moderately differentiated colonic adenocarcinomas (20/20). In the normal colonic mucosa, survivin expression was mostly restricted to the base of the colonic crypts. All epithelial cells showed uniformly intense staining for survivin in hyperplastic polyps. By contrast, adenomas and adenocarcinomas showed a heterogeneous staining pattern with cell-to-cell, gland-to-gland, and regional variability in the intensity of survivin staining. In contrast to the basal preponderance of staining in normal colonic mucosa, numerous survivin positive cells were present at the luminal surface of hyperplastic polyps, adenomatous polyps, and adenocarcinomas. In conclusion, the expression of survivin is not a specific marker of adenocarcinoma of the colon but does show characteristic and reproducible patterns of expression in non-neoplastic proliferative lesions and in normal colonic mucosa.

Phenotypic and molecular characteristics of hyperplastic polyposis

BACKGROUND & AIMS

Patients with hyperplastic polyposis are reported to have multiple and/or large hyperplastic polyps (HPs) and an increased risk of colorectal cancer, but the phenotype and genetic alterations in hyperplastic polyposis have not been studied in detail.

METHODS

We evaluated clinical-pathological and molecular characteristics of 129 HPs, 6 serrated adenomas, and 3 admixed hyperplastic-adenomatous polyps from 13 patients with hyperplastic polyposis (more than 20 HPs), 5 patients with a large HP (>/=1 cm in diameter), and 5 patients with multiple HPs (5-10 HPs).

RESULTS

HPs in the right colon in contrast to the left colorectum had more frequent topographic dysregulation of p21(Waf-1/Cip1) expression (94% vs. 76%, P = 0.03) and of proliferation (92% vs. 53%, P = 0. 0001), but less frequent allelic loss of chromosome 1p (4% vs. 17%, P = 0.03). K-ras mutation was present in 8% of HPs, p53 gene product overexpression in none, and microsatellite instability in 3% without relationship to microsatellite instability in synchronous cancer. Patients with a large HP differed from those with multiple HPs in having a high frequency of right-sided HP (63% vs. 22%, P = 0.01) and of right-sided colon cancer (100% vs. 8%, P = 0.003). Hyperplastic polyposis was associated with a family history of colorectal cancer (P = 0.01) and with loss of chromosome 1p in HP (21% vs. 0%, P = 0.001).

CONCLUSIONS

A hyperplastic polyp/dysplasia-to-adenocarcinoma sequence can be manifested in 3 distinct phenotypes consisting of patients with hyperplastic polyposis and chromosome 1p allelic loss in some HPs, in contrast to patients who have large, right-sided HPs or small numbers of HPs that lack 1p loss.

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.

Multiple 'serrated adenocarcinomas' of the colon with a cell lineage common to metaplastic polyp and serrated adenoma. Case report of a new subtype of colonic adenocarcinoma with gastric differentiation

A 70-year-old woman underwent right hemicolectomy and six carcinomas were recognized in the resected colon. These carcinomas were considered to be of a cell lineage common to serrated adenoma (SA) and hyperplastic (metaplastic) polyp (H/MP), because of the occurrence of multiple SAs and H/MPs around the carcinomas, as well as the co-existence of SA and H/MP areas within the carcinomas. These carcinomas had the following common histological and immunohistochemical features: a serrated structure resembling SA; a lace-like structure; infiltrative growth within the muscularis propria, with dedifferentiation at the invasive front; and immunohistochemical expression of pS2 and human gastric mucin. Based on these features, a new subtype of carcinoma is proposed, with a cell lineage common to SA and H/MP. It would also seem that p53 is involved in the serrated adenoma-carcinoma sequence.

The differentiation of true adenomas from colitis-associated dysplasia in ulcerative colitis: a comparative immunohistochemical study

Adenomas in areas involved by ulcerative colitis (UCA) are difficult to identify because of their morphological similarity to ulcerative colitis-associated dysplasia (UCD) and have an uncertain biology. Recently, a set of morphopathologic criteria were published for the diagnosis of UCA versus UCD. As a first step to analyze these criteria, we studied p53 and bcl-2 expression in groups of UCA and UCD along with a sporadic adenoma control group. Ninety lesions from UC areas (62 patients) were examined, including 24 UCA without high-grade dysplasia (HGD) and 66 UCD consisting of 43 polypoid and 23 flat dysplastic lesions (29 with HGD). Immunohistochemical p53 and bcl-2 expression were evaluated semiquantitatively. P53-positive cases were significantly less frequent in the UCA (4%) versus the UCD group (30%, P = .01) and the polypoid UCD subgroup (35%, P = .005). Moderate or strong bcl-2 expression was significantly more frequent in the UCA than in the UCD group (96% v 70%, P = .01) and in the UCA versus both polypoid and flat UCD subgroups. Comparison of UCA with low-grade dysplastic polypoid UCD cases alone showed a difference just below significance for p53 (P = .07). p53 and bcl-2 expression rates were very similar in the UCA group and the sporadic adenoma (n = 25) control group. These results show that UCA has phenotypic features more similar to sporadic adenomas than UCD and supports the concept that adenomas in UC have a biology different from UC-associated dysplasia.

Cell kinetics, p53 and bcl-2 expression, and c-Ki-ras mutations in flat-elevated tubulovillous adenomas and adenocarcinomas of the colorectum: comparison with polypoid lesions

BACKGROUND

Flat(-elevated) tubulovillous adenomas and adenocarcinomas of the colorectum constitute a specific type of neoplasm with superficial spreading growth. To establish their characteristics, a comparative investigation of a series of tumors was performed.

METHODS

A total of 56 flat tubulovillous tumors (39 adenomas, 17 invasive carcinomas) and 154 polypoid tubular or villous tumors (77 adenomas, 77 invasive carcinomas) were comparatively assessed for cell kinetics and molecular alterations.

RESULTS

Ki-67 labeling and p53 expression for both types of tumors increased along with degree of dysplasia or invasion, whereas bcl-2 expression showed an inverse decrease. However, apoptotic activity was invariably low in the flat tubulovillous tumors, as compared with the polypoid tumors, in which increase was apparent with tumor progression. The flat tubulovillous tumors also showed a higher frequency of c-Ki-ras mutations (92.9%) than the polypoid tubular tumors (40.0%).

CONCLUSIONS

The flat tubulovillous tumor can be considered a distinct entity, with characteristics different from the polypoid counterpart.

Clinicopathological features of serrated adenoma of the colorectum: comparison with traditional adenoma

AIM

Serrated adenoma is a recently described category of colorectal adenoma. The aim of this study was to determine whether serrated adenomas have clinicopathological findings distinct from "traditional" adenoma.

METHODS

Colonoscopy records for 1995-1998 were reviewed, and all traditional adenomas and serrated adenomas identified. Tumour site and endoscopic configuration were compared between the two types of adenoma. In polypectomised lesions, size and grade of dysplasia were compared between the two groups.

RESULTS

There were 3305 traditional adenomas and 43 serrated adenomas. Serrated adenomas were more often found in the rectosigmoid colon than the traditional adenomas (67.5% v 41.2%, p = 0.0008). Polypectomy was more often done for serrated adenomas (27 of 43 lesions, 62.8%) than for traditional adenomas (626 of 3305 lesions, 18.9%, p < 0.0001). Size (mean (SD) maximum dimension, 12 (6) mm v 13 (3) mm) and incidence of high grade dysplasia (14.8% v 13.6%) in endoscopically removed specimens were not different between the two types.

CONCLUSIONS

The therapeutic judgement applied to the management of traditional adenoma seems to be appropriate for serrated adenoma.

Serrated adenoma of the colorectum: colonoscopic and histologic features

BACKGROUND

Serrated adenoma is a recently recognized epithelial neoplasm of the colorectum. The aim of this study is to clarify the colonoscopic features of serrated adenomas.

METHODS

The endoscopic findings for 52 serrated adenomas of the colorectum were investigated; these were then divided into three groups according to surface features. The histologic type (tubular, tubulovillous or villous) and the incidence of high-grade dysplasia were compared among the three groups.

RESULTS

The surface under chromoscopy showed a hyperplastic pattern in 17 lesions, a cerebriform pattern in 18 lesions and a combined pattern in 17 lesions. The tubular type of serrated adenoma was predominant in the hyperplastic pattern group (94%), whereas the tubulovillous or villous histologic types were frequent in the cerebriform pattern (89%) and combined pattern (82%) groups. High-grade dysplasia was found in 18% of the combined pattern adenomas; the incidence was lower in hyperplastic (6%) or cerebriform pattern (0%) adenomas.

CONCLUSIONS

Surface features of serrated adenomas have a close correlation with their histologic type. A combined hyperplastic-cerebriform surface pattern under chromoscopy was seen only in serrated adenomas.

'Serrated' adenoma of the colorectum, with reference to its gastric differentiation and its malignant potential

Serrated adenoma of the colorectum was a newly proposed entity in 1990, characterized by epithelial neoplasia combining the architectural features of a hyperplastic (metaplastic) polyp with the cytological features of an adenoma. Its histogenesis and natural history still remain unclear. Forty-six serrated adenomas were obtained from 46 patients. The clinicopathological features were summarized. Paraffin-embedded blocks from 34 serrated adenomas were available for immunohistochemical studies using pS2, human gastric mucin, and p53 protein. Eighteen hyperplastic (metaplastic) polyps, 16 tubular adenomas, and 12 early-stage adenocarcinomas were randomly selected as control groups for immunohistochemical analysis. The patients' ages ranged from 32 to 86 (average 61.4) years. Males were more frequently affected than females. Serrated adenomas were predominantly present in the left-side of the colon and in the rectum (72 per cent). Their sizes ranged from 3 to 26 mm (average 9. 2mm). Six lesions (13 per cent) contained foci of high-grade dysplasia. These adenomas were significantly larger (12.7 mm) than those containing no high-grade dysplasia (8.6mm). pS2 and human gastric mucin were expressed significantly more frequently in both hyperplastic (metaplastic) polyps and serrated adenomas than in tubular adenomas or adenocarcinomas. p53-positive cells were present in 18 of the 29 pure serrated adenomas (62 per cent) and in one of the five areas of low-grade dysplasia in serrated adenomas with high-grade dysplasia (20 per cent), most of which revealed a sporadic distribution. Only five of the 29 serated adenomas with no high-grade dysplasia (17 per cent) were regarded as demonstrating p53 overexpression. On the other hand, three of the five areas of high-grade dysplasia in serrated adenomas (60 per cent) revealed diffuse positivity (3+) for p53 protein. The serrated adenoma, which possibly shows gastric differentiation, is considered to be an independent histological entity among the various phenotypes of colorectal adenomas. Serrated adenoma would seem to be a precursor of carcinoma, its potential for malignant transformation being similar to that of the traditional tubular adenoma. It would also seem that p53 is involved in the serrated adenoma-carcinoma sequence.

Clear cell change in colorectal adenomas: its incidence and histological characteristics

AIMS

The aim of our investigation was to clarify the histological characteristics and biological significance of clear cell change in colorectal adenomas. METHODS ANID RESULTS: We found three cases (0.086%) of tubular adenomas with clear cell change in a review of 3486 cases of colorectal adenoma. These three cases occurred in male patients and were located in the left-sided colon. To investigate the nature and biological significance of the clear cells, we conducted histochemical staining (periodic acid-Schiff (PAS) with or without diastase digestion, alcian blue pH 2.5) and immunohistochemical staining (using antibodies against carcinoembryonic antigen (CEA), alpha-fetoprotein, p53 protein and Ki67 antigen) and also mitotic counts. Histologically, the changed area was characterized by pyknotic and randomly arranged nuclei with PAS-negative clear and vacuolated cytoplasm. Immunoreactivity for CEA was diffuse and strong in the clear cells, but not in the tumour cells in the ordinary portion of the adenomas. The Ki67 labelling index and the mitotic activity were both higher in the clear cell portion than in the ordinary portion.

CONCLUSIONS

This is the first study to indicate the incidence of clear cell change among colorectal adenomas. It has confirmed high proliferative activity within the clear cell portion of colorectal adenomas.

Immunohistochemical analysis of a case of gastritis cystica profunda associated with carcinoma development

We report a rare case of gastritis cystica profunda (GCP) accompanied by carcinoma that developed in a 51-year-old Japanese man without antecedent gastric surgery. The polypoid tumor was located in the upper body of the resected stomach. Histologically, it was characterized by herniation of surface epithelium and cystic glands in the submucosa, muscularis propria, and subserosa. Marked chronic atrophic gastritis was found throughout the stomach, and dysplastic epithelia and a few adenocarcinoma cells were found in the deeper parts of the GCP. The Ki-67, p53, and p21WAF1/CIP1 labeling indices for the deeper part of the GCP were higher than those for the superficial parts or the surrounding mucosa, suggesting that both epithelial cell proliferation and p53-dependent p21WAF1/CIP1 expression in DNA-damaged cells, which might be associated with gastritis, are enhanced in line with penetration of glands. The underlying mechanisms might be linked in a chain of factors leading to malignancy.