Adenocarcinoma of colon differentiating as dome epithelium of gut-associated lymphoid tissue

Family adenomatous polyposis come across dome type adenocarcinoma: a case report and literature review

Dome-type carcinoma (DC), also referred as Gut-associated lymphoid tissue (GALT) carcinoma, is a rare variant of colorectal adenocarcinoma which has been seldomly reported up to now. We report a case of a DC lesion developed in a 33-year-old male diagnosed with family adenomatous polyposis (FAP). A 1.5 × 1.5 cm well-demarcated lesion exhibited a 0-Is + IIc figure was detected near the anastomotic stoma during regular colonoscopic polypectomy. Surgical specimen showed well-differentiated adenocarcinoma consisted of dilated cystic glands and the lymphoid stroma with reactive germinal centers exhibited a destructive manner of infiltration into SM2 level. The immunohistochemical findings revealed MUC1 positive but MUC2 negative of the carcinomas epithelial which retained all the 4 mismatch repair proteins (MMRs) (MLH1, PMS2, MSH2, and MSH6) and was negative for EBV-encoded small RNA-1 (EBER). Considered a rare category of colorectal adenocarcinoma, more cases will help uncover the nature of GALT/dome-type carcinoma. Clinicians and pathologists should be aware of recognizing this special type of carcinoma and making necessary differential diagnostics.

Rare Case of Gut-associated Lymphoid Tissue Carcinoma in the Sigmoid Colon of a Very Elderly Patient: A Case Report

Colorectal cancer with gut-associated lymphoid tissue (GALT) carcinoma histopathology is particularly rare in very elderly patients. GALT is characterized by submucosal localization and prominent lymphoid infiltration with germinal center formation within tumor-infiltrating lymphocytes. This study aims to report a case of colorectal cancer with GALT carcinoma histopathology in a very elderly patient and to provide a comprehensive literature review. In this case, a 90-year-old female presented with an irregularly elevated tumor in the sigmoid colon, diagnosed via colonoscopy. Computed tomography revealed no lymph node or distant metastases. The patient underwent laparoscopy-assisted sigmoid colon resection with D3 dissection. Histopathological examination revealed well-differentiated adenocarcinoma in the submucosal layer with partial invasion into the muscle layer. Lymphocytes, along with lymph follicles, proliferated compressively in the stroma surrounding the tumor glands. Immunohistochemical analysis showed lost expression of mismatch repair proteins, MLH1 and PMS2, consistent with the tumor immunohistochemistry profile. B cells (CD20- and CD79a-positive) were generally distributed in and around the lymph follicles, while T cells (CD3-positive) were primarily located between the lymph follicles. This case highlights the rare histopathology of GALT carcinoma in colorectal cancer and underscores the importance of considering such diagnoses in elderly patients with colorectal tumors.

Zearalenone-14-glucoside specifically promotes dysplasia of Gut-Associated Lymphoid Tissue: A natural product for constructing intestinal nodular lymphatic hyperplasia model

INTRODUCTION

Zearalenone-14-glucoside (Z14G) is a modified mycotoxin that widely contaminates food across the world. Our preliminary experiment showed that Z14G degrades to zearalenone (ZEN) in the intestine exerting toxicity. Notably, oral administration of Z14G in rats induces intestinal nodular lymphatic hyperplasia.

OBJECTIVES

To investigate the mechanism of Z14G intestinal toxicity and how it differs from ZEN toxicity. We conducted a precise toxicology study on the intestine of rats exposed to Z14G and ZEN using multi-omics technology.

METHODS

Rats were exposed to ZEN (5 mg/kg), Z14G-L (5 mg/kg), Z14G-H (10 mg/kg), and pseudo germ free (PGF)-Z14G-H (10 mg/kg) for 14 days. Histopathological studies were performed on intestines from each group and compared. Metagenomic, metabolomic, and proteomic analyses were performed on rat feces, serum, and intestines, respectively.

RESULTS

Histopathological studies showed that Z14G exposure resulted in dysplasia of gut-associated lymphoid tissue (GALT) compared to ZEN exposure. The elimination of gut microbes in the PGF-Z14G-H group alleviated or eliminated Z14G-induced intestinal toxicity and GALT dysplasia. Metagenomic analysis revealed that Z14G exposure significantly promoted the proliferation of Bifidobacterium and Bacteroides compared to ZEN. Metabolomic analysis showed that Z14G exposure significantly reduced bile acid, while proteomic analysis found that Z14G exposure significantly reduced the expression of C-type lectins compared to ZEN.

CONCLUSIONS

Our experimental results and previous research suggest that Z14G is hydrolyzed to ZEN by Bifidobacterium and Bacteroides promoting their co-trophic proliferation. This leads to inactivation of lectins by hyperproliferative Bacteroides when ZEN caused intestinal involvement, resulting in abnormal lymphocyte homing and ultimately GALT dysplasia. It is noteworthy that Z14G is a promising model drug to establish rat models of intestinal nodular lymphatic hyperplasia (INLH), which is of great significance for studying the pathogenesis, drug screening and clinical application of INLH.

Gut-associated Lymphoid Tissue/Dome-Type Carcinoma of the Colon: A Rare Case Report With Review of the Literature

Gut-associated lymphoid tissue (GALT) carcinoma, also termed dome-type carcinoma, is an infrequent distinctive subtype of colorectal adenocarcinoma and only 18 cases have been reported in the English medical literature. These tumors have unique clinicopathological features and are considered to have a low malignant potential with favorable prognosis. Herein, we described a case of a 49-year-old male with intermittent hematochezia for 2 years. Colonoscopy revealed a sessile broad-based polyp of approximately 20 mm × 17 mm in the sigmoid colon 260 mm away from the anus, with a slightly hyperemic surface. Histologically, this lesion showed typical GALT carcinoma. The patient was followed up for one and a half year and he did not experience any discomfort, such as abdominal pain or hematochezia, and no tumor recurrence occurred. Moreover, we reviewed the literature, summarized the clinicopathological features of GALT carcinoma, and highlighted its pathological differential diagnosis to further explore this infrequent type of colorectal adenocarcinoma.

Dome-type carcinoma of the rectum mimicking a submucosal tumor: a case report and literature review

Dome-type carcinoma (DC) has been recognized as a rare variant of adenocarcinoma, which arises in gut-associated lymphoid tissue. It has a specific morphologic feature of a dome-like protrusion associated with lymphoid tissue. We report a case of a DC of the rectum in an asymptomatic 58-year-old male. A 2-cm sized, well-demarcated, round mass masquerading as a submucosal tumor (SMT) was identified in the rectum and was resected by endoscopic submucosal dissection. The tumor was revealed as an adenocarcinoma with submucosal invasion of 3,700 µm, which consisted of dilated cystic glands and the lymphoid stroma with reactive germinal centers. On immunohistochemistry, the tumor cells revealed retained expression for mismatch repair proteins. Laparoscopic surgical resection was subsequently performed. DC is considered a distinctive subtype of colorectal adenocarcinoma with characteristic morphology and low-grade malignant potential. Careful detection of the overlying mucosal lesion is crucial to differentially diagnose DC from SMT.

Whole exome sequencing of a gut-associated lymphoid tissue neoplasm points to precursor or early form of sporadic colon carcinoma

Gut-associated lymphoid tissue (GALT) carcinoma is a colorectal neoplasm characterized by cystically dilated neoplastic glands that extend into prominent, well-circumscribed submucosal lymphoid tissue. Although often subtle, lamina propria between and around the neoplastic glands (identified by plasma cells, scattered eosinophils, etc.) is frequent in cases with classic morphology, arguing (at least in such cases) in favor of adenoma extending into lymphoglandular complexes rather than true invasive carcinoma. Some have postulated that the tumor arises from M-cells, specialized epithelial cells overlying GALT, and others have suggested it represents a unique pathway to carcinoma, specific to the environmental conditions of epithelium overlying lymphoid tissue. Although both hypotheses are intriguing, definitive phenotypic and genetic support is currently lacking. To address these possibilities, we undertook whole exome sequencing and immunohistochemical characterization of a GALT neoplasm recently identified on our clinical service. We discovered well-known mutations in both APC and KRAS, as well as mutations in several Wnt pathway components (MED12, BCL9L, RFX4, DACT3). No immunohistochemical expression of GP2, a marker of M-cell differentiation, was identified. Expression of CDX2, SATB2, and the DNA mismatch repair proteins was observed, while expression of both CK7 and CK20 was absent. No PD-L1 expression was present on tumor cells, but PD-L1 expression was noted in a subset of tumor-adjacent mononuclear cells. Overall, the findings suggest that GALT neoplasms, although morphologically distinct, may be a precursor or early form of typical sporadic colon carcinoma.

Colorectal epithelial neoplasm associated with gut-associated lymphoid tissue

BACKGROUND

Colorectal epithelial neoplasm extending into the submucosal gut-associated lymphoid tissue (GALT) can cause difficulties in the differential diagnosis. Regarding GALT-associated epithelial neoplasms, a few studies favor the term "GALT carcinoma" while other studies have mentioned the term "GALT-associated pseudoinvasion/epithelial misplacement (PEM)".

METHODS

The clinicopathologic characteristics of 11 cases of colorectal epithelial neoplasm associated with submucosal GALT diagnosed via endoscopic submucosal dissection were studied.

RESULTS

Eight cases (72.7%) were in males. The median age was 59 years, and age ranged from 53 to 73. All cases had a submucosal tumor component more compatible with GALT-associated PEM. Eight cases (72.7%) were located in the right colon. Ten cases (90.9%) had a non-protruding endoscopic appearance. Nine cases (81.8%) showed continuity between the submucosal and surface adenomatous components. Nine cases showed (81.8%) focal defects or discontinuation of the muscularis mucosae adjacent to the submucosal GALT. No case showed hemosiderin deposits in the submucosa or desmoplastic reaction. No case showed single tumor cells or small clusters of tumor cells in the submucosal GALT. Seven cases (63.6%) showed goblet cells in the submucosa. No cases showed oncocytic columnar cells lining submucosal glands.

CONCLUSIONS

Our experience suggests that pathologists should be aware of the differential diagnosis of GALT-associated submucosal extension by colorectal adenomatous neoplasm. Further studies are needed to validate classification of GALT-associated epithelial neoplasms.

Gut-associated lymphoid tissue or so-called “dome” carcinoma of the colon: Review

AIM

To present a comprehensive review of the etiology, clinical features, macroscopic and pathological findings, and clinical significance of Gut-associated lymphoid tissue or “dome” carcinoma of the colon.

METHODS

The English language medical literature on gut- or gastrointestinal-associated lymphoid tissue (GALT) or “dome” carcinoma of the colon was searched and appraised.

RESULTS

GALT/dome-type carcinomas of the colon are thought to arise from the M-cells of the lymphoglandular complex of the intestine. They are typically asymptomatic and have a characteristic endoscopic plaque- or “dome”-like appearance. Although the histology of GALT/dome-type carcinomas displays some variability, they are characterized by submucosal localization, a prominent lymphoid infiltrate with germinal center formation, tumor-infiltrating lymphocytes, absence of desmoplasia, and dilated glands lined by columnar epithelial cells with bland nuclear features and cytoplasmic eosinophilia. None of the patients reported in the literature with follow-up have developed metastatic disease or local recurrence.

CONCLUSION

Increased awareness amongst histopathologists of this variant of colorectal adenocarcinoma is likely to lead to the recognition of more cases.

GALT carcinoma: three case reports with glycoprotein 2 immunohistochemistry and electron microscopic observations

AIMS

Gut-associated lymphoid tissue (GALT) carcinoma is a rare colorectal tumour that arises in the epithelium covering GALT. GALT carcinoma is a differentiated tubular adenocarcinoma with dense lymphoid tissue with a characteristically well-demarcated margin. To date, 26 cases of GALT carcinoma, including the three cases discussed here, have been reported. Most (24 of 26) were discovered at early stages and none of the cases have documented any metastases. This suggests that GALT carcinoma may have a favourable prognosis. It is hypothesised that GALT carcinoma originates from M cells in specialised epithelia covering GALT. However, this hypothesis has yet to be confirmed.

METHODS AND RESULTS

In this study, we examined three cases of GALT carcinoma by immunohistochemistry detection of glycoprotein 2, a specific marker for M cells, and electron microscopy. Our findings showed that the tumour cells of GALT carcinoma in all three cases were negative for M cells. We thus concluded that GALT carcinoma may be a tubular adenocarcinoma arising by chance in the GALT. This unique carcinoma is a diferentiated adenocarcinoma that grows slowly with the development of GALT.

CONCLUSIONS

We propose that GALT carcinoma should be classified separately because of its histological setting and good prognosis.

The third pathway of colorectal carcinogenesis

Aims

The majority of the colorectal carcinomas (CRC) arise in a vast mucosal area built with columnar cells and mucus-producing goblet cells. These carcinomas evolve via the conventional (tubular/villous) adenoma–carcinoma pathway, or the serrated adenoma–carcinoma pathway. Much less frequently CRC arise in the gut-associated lymphoid tissue (GALT) mucosal domain via the third pathway of colorectal carcinogenesis.

Methods

All publications on human colorectal GALT carcinomas in the literature were reviewed.

Results

Only 23 GALT-carcinomas found in 20 patients are in record. The GALT carcinomas were detected at surveillance colonoscopic biopsy in 11 patients (four had ulcerative colitis, two were members of a Lynch syndrome family, two of a CRC family, one had familial adenomatous polyposis (FAP), one prior colon adenomas and one a submucosal tumour), or at diagnostic colonoscopic biopsy in the remaining nine patients (three had rectal bleedings, two abdominal pains, one diverticular disease and one protracted constipation. In three, no ground disease or symptoms were provided). In six of the 23 GALT carcinomas, the luminal surface showed tumour cells, ulcerations or no descriptions were given. Ten (66.7%) of the remaining 15 GALT carcinomas showed on top, adenomas (n=8) or high-grade dysplasia (n=2).

Conclusions

The low frequency of GALT carcinomas might be explained by the fact that the colorectal mucosal areas occupied by GALT domains are minute. The finding that two-thirds of the 15 remaining GALT carcinomas (vide supra) were covered by high-grade dysplasia or by conventional adenomas strongly suggest that conventional non-invasive neoplasias might have preceded the majority of the GALT carcinomas in record.

Azadircta indica as a modulator of membrane stability parameters and surface changes during 1,2 dimethylhydrazine-induced colorectal carcinogenesis

OBJECTIVE

The aim of the present study was to study the modulatory potential of Azadirta indica on colonic surface abnormalities and membrane fluidity changes following 1,2 dimethylhydrazine-induced [DMH] colon carcinogenesis.

MATERIALS AND METHODS

Brush border membranes [BBM] were isolated from the colon of rats and the viscosity as well as fluidity parameters were assessed by using the membrane extrinsic fluorophore pyrene.

RESULTS

DMH treatment resulted in a significant increase in lipid peroxidation [LPO]. Reduced glutathione levels [GSH] and the activities of glutathione reductase [GR], glutathione transferase [GST], superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GPx] were found to be significantly decreased following DMH treatment. On the other hand, supplementation with AI, DMH-treated rats resulted in a significant decrease in the levels of lipid peroxidation but caused a significant increase in the levels of GSH as well in the activities of GR, GST, SOD, CAT and GPx. The results further demonstrated a marked decrease in membrane microviscosity following DMH treatment. On the other hand, a significant increase was observed in the excimer/monomer ratio and fluidity parameter of DMH-treated rats when compared to normal control rats. However, the alterations in membrane microviscosity and the fluidity parameters were significantly restored following A. indica treatment. Further, histological as well as colon surface alterations were also observed following DMH treatment, which however were greatly prevented upon AI co-administration.

CONCLUSIONS

The study, therefore, concludes that A. indica proves to be useful in modulating the colonic surface abnormalities and membrane stability following DMH-induced colon carcinogenesis.

Colon adenocarcinoma with dome-like phenotype: characteristic endoscopic ultrasonography (EUS) findings

An 80-year-old man underwent colonoscopy for proctorrhagia. Conventional white-light imaging showed a superficially flat and elevated lesion that appeared to be a submucosal tumor of the sigmoid colon. Chromoendoscopy with Indigo Carmine showed that the margin of the tumor was covered with normal epithelium but that there was a slight depression on its surface. Magnification endoscopy with Crystal Violet staining revealed the amorphous surface structure of the depressed lesion, but the surrounding mucosa showed a normal pit pattern. Endoscopic ultrasonography demonstrated that a hypoechoic mass was located in the submucosal layer, and a biopsy specimen obtained from the surface of the lesion showed evidence of adenocarcinoma. We then performed sigmoidectomy on the patient. Immunohistochemically, the tumor cells were positive for two mismatch repair proteins (MLH1 and MSH2), but in situ hybridization revealed that the specimen was negative for the Epstein - Barr virus. We finally diagnosed the lesion as adenocarcinoma with a dome-like phenotype of the sigmoid colon.

DOME/GALT type adenocarcimoma of the colon: a case report, literature review and a unified phenotypic categorization

Several types of colorectal cancers are associated with a prominent lymphoid component, which is considered a positive prognostic factor. We report a case of a dome-type carcinoma of the cecum in a 57 year old female. The sessile, non-polypoid lesion histologically consisted of a tubulovillous adenoma with low-grade dysplasia. The submucosal invasive component showed low-grade architectural features that included cystically dilated glands containing eosinohilic debris. Immunohistochemical studies displayed retention of the four mistmach repair proteins, consistent with a stable phenotype. After 3 years, the patient remains free of recurrence. A literature review highlighted striking similarities between dome-type carcinoma and the gut-associated lymphoid tissue carcinoma, the two sharing an intimate association with the gut associated lymphoid tissue.The two variants might therefore be grouped into a unified category.

S100P, a calcium-binding protein, is preferentially associated with the growth of polypoid tumors in colorectal cancer

Colorectal cancer (CRC) is a genetically heterogeneous disease with distinct morphological patterns. It has been shown that polypoid and ulcerative CRC displays different genetic alterations. In the present study, we aimed to investigate genes with differential expression patterns between ulcerative and polypoid CRC. cDNA microarray analysis was performed to compare the gene expression profiles in samples of ulcerative and polypoid CRC with paired normal mucosa samples. Potential candidate genes were further validated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), western blot analysis and immunohistochemistry. The epigenetic regulation of gene expression was investigated using methylation-specific PCR (MSP). cDNA microarray analysis identified 11 upregulated and 14 downregulated genes which were differentially expressed in samples from both tumor types compared to the matched normal mucosa samples. Among these, S100P was the only upregulated gene preferentially associated with polypoid CRC (P=0.032). The samples of polypoid CRC displayed significantly higher S100P protein and mRNA expression levels than the samples of ulcerative CRC (P<0.05, respectively). Using semi-quantitative immunohistochemical analyses, S100P overexpression was found to be preferentially associated with polypoid CRC (24/30 vs. 14/40, P<0.001). The relative methylation level determined by MSP did not differ significantly between the samples of polypoid and ulcerative CRC (43.36 vs. 49.10%, P=0.168), indicating that promoter hypomethylation was not directly related to the upregulation of S100P mRNA. Our results demonstrate that the upregulation of S100P mRNA and protein expression is a predominant characteristic in polypoid CRC, whereas ulcerative CRC presents with a wide range of expression levels, indicating that S100P overexpression is not a key determinant in conferring invasion properties. The clinicopathological significance of S100P in CRC requires further investigation in well-controlled studies.

Dome-type: a distinctive variant of colonic adenocarcinoma

Introduction. Ten cases of dome-type adenocarcinoma of the colon have been reported so far. Most of them were presented as early lesions, with endoscopic and microscopic distinguishing features. Methods and Results. A raised plaque was removed from the right colon during colonoscopy in a 56-year-old man. Histopathological examination showed a cancerized adenoma invading the submucosa with several typical features of dome-type adenocarcinoma, in particular the associated prominent lymphoid tissue. Immunohistochemistry showed retention of the mismatch repair proteins MLH-1, MSH-2, MLH-6, and PMS-2. Conclusion. We report an additional case of dome-type adenocarcinoma of the colon as an early, low-risk, and microsatellite stable tumor, indicating that this particular histotype may deserve specific consideration for both classification and management.

Dome-type carcinoma of the colon; a rare variant of adenocarcinoma resembling a submucosal tumor: a case report

Background

Dome-type carcinoma (DC) is a distinct variant of colorectal adenocarcinoma and less than 10 cases have been described in the literature. Most of the previously reported cases were early lesions and no endoscopic observations have been described so far. We herein report a case of a DC invading the subserosal layer, including endoscopic findings.

Case presentation

A highly elevated lesion in the transverse colon was diagnosed by colonoscopy in a 77-year-old man. The tumor appeared to be similar to a submucosal tumor (SMT), however, a demarcated area of reddish and irregular mucosa was observed at the top of the tumor. There were no erosions or ulcers. Laparoscopic-assisted right hemicolectomy was performed and pathological examination revealed a well-circumscribed tumor invading the subserosal layer. The tumor was a well-differentiated adenocarcinoma associated with a dense lymphocytic infiltration and showed expansive growth. The overlying mucosal layer showed high-grade dysplasia.

Conclusion

The present lesion was diagnosed as a DC of the colon invading the subserosal layer. Because the association of mucosal dysplasia is common in DCs, the detection of dysplastic epithelium would be important to discriminate DCs from SMTs.

The mucosa beyond the polyps in juvenile polyposis

Little is known of early histologic changes in the mucosa of the colon aside from the polyps in Juvenile Polyposis. Provided with a surgical specimen of a total colectomy of a 6-year-old boy with this condition, this report describes those changes. The mucosa depicted a peculiar serrated profile of the uppermost part of the crypts due to elongation of them, dilated openings, and scant stroma. Also present were frequent aberrant crypts. Early juvenile polyps presented associated with lympho-glandular sites as distorted and microcystically dilated crypts containing granular and filamentous mucoid material. The findings possibly represent the abnormal cytologic potential of this genetic condition.

Colorectal carcinoma with dome-like phenotype: an under-recognised subset of colorectal carcinoma?

BACKGROUND

The term dome carcinoma has been applied to a variant of colorectal carcinoma, thought to derive from M-cells of the gut-associated lymphoid tissue. Its distinguishing morphological features include a non-polypoid plaque-like lesion composed of closely apposed cystically dilated glands lined by a single layer of non-mucinous cells, intensely PAS-positive intraluminal material, and a close spatial relation to lymphoid stroma.

AIMS AND METHODS

A search in the literature for such cases and the authors' experience with carcinomas sharing morphological details with dome carcinoma are presented to direct focus on this unique phenotype of colorectal carcinoma and to expand on its morphology.

RESULTS

Four such examples, all stage pT1, pN0 have been previously reported. Here two additional cases, with several features of dome carcinoma, stage pT1 and pT2, respectively, are added. An extensive intramucosal component, unassociated with adenomatous growth, a pink quality of the lesional cells, low grade budding, absence of cytoplasmic pseudofragments, and absence of necrosis characterised the present cases as well as intact MMR-proteins and loss of APC. As opposed to two of the previously reported cases, intraepithelial lymphocytes were unapparent in these cases and the lymphoid stroma was effaced along with tumour progression in one of the present cases. Hence, a range of appearances is encompassed by the dome carcinoma. The uncommon reporting of dome carcinoma may be due to lack of awareness of this particular subset of colorectal carcinoma. Indeed, one of the current cases was signed out as a conventional carcinoma, despite the comment in the pathology report of an unusual morphology.

CONCLUSION

Dome carcinoma may be more under-recognised than rare. The reporting of variants of colorectal carcinoma, displaying histological features suggestive of dome carcinoma, is encouraged in order to obtain more exact knowledge on its putative clinical significance.

Ligand activation of peroxisome proliferator-activated receptor beta inhibits colon carcinogenesis

There is considerable debate whether peroxisome proliferator-activated receptor beta/delta (PPARbeta/delta) ligands potentiate or suppress colon carcinogenesis. Whereas administration of a PPARbeta ligand causes increased small intestinal tumorigenesis in Apc(min/+) mice, PPARbeta-null (Pparb-/-) mice exhibit increased colon polyp multiplicity in colon cancer bioassays, suggesting that ligand activation of this receptor will inhibit colon carcinogenesis. This hypothesis was examined by treating wild-type (Pparb+/+) and Pparb-/- with azoxymethane, coupled with a highly specific PPARbeta ligand, GW0742. Ligand activation of PPARbeta in Pparb+/+ mice caused an increase in the expression of mRNA encoding adipocyte differentiation-related protein, fatty acid-binding protein, and cathepsin E. These findings are indicative of colonocyte differentiation, which was confirmed by immunohistochemical analysis. No PPARbeta-dependent differences in replicative DNA synthesis or expression of phosphatase and tensin homologue, phosphoinositide-dependent kinase, integrin-linked kinase, or phospho-Akt were detected in ligand-treated mouse colonic epithelial cells although increased apoptosis was found in GW0742-treated Pparb+/+ mice. Consistent with increased colonocyte differentiation and apoptosis, inhibition of colon polyp multiplicity was also found in ligand-treated Pparb+/+ mice, and all of these effects were not found in Pparb-/- mice. In contrast to previous reports suggesting that activation of PPARbeta potentiates intestinal tumorigenesis, here we show that ligand activation of PPARbeta attenuates chemically induced colon carcinogenesis and that PPARbeta-dependent induction of cathepsin E could explain the reported disparity in the literature about the effect of ligand activation of PPARbeta in the intestine.

HNPCC and sporadic MSI-H colorectal cancer: a review of the morphological similarities and differences

Morphological features may serve as diagnostically useful markers of colorectal cancer (CRC) with the microsatellite instability-high (MSI-H) phenotype. The most important of these are lymphocytic infiltration, mucin secretion and poor differentiation. These features are apparent in both sporadic MSI-H CRC and CRC occurring in the context of hereditary non-polyposis colorectal cancer (HNPCC). There is now strong evidence that that the two principal subtypes of MSI-H CRC evolve through different pathways. Sporadic MSI-H CRC orginate within serrated polyps with BRAF mutation and DNA methylation while CRC in HNPCC arise within conventional adenomas in which there is frequent mutation of APC or beta -catenin and/or K- ras. These early differences in pathogenesis translate into multiple morphological distinctions in the cancers developing through the two pathways. Lymphocytic infiltration, tumour budding (de-differentiation), and co-existing adenomas are more evident in HNPCC while mucin secretion, poor differentiation, tumour heterogeneity and glandular serration, and co-existing serrated polyps are more evident in sporadic MSI-H CRC. Sporadic MSI-H CRC are also characterized by cytoplasmic eosinophilia and nuclei that are large, round, vesicular and contain a prominent nucleolus while in HNPCC the cytological features recapitulate the basophilia and nuclear characteristics of conventional adenomas. In practice, lymphocytic infiltration is the most sensitive marker of MSI-H status in both sporadic CRC and HNPCC. The crucial distinction between HNPCC and sporadic MSI-H CRC should be achieved by means of all available data including family history, age at onset of malignancy and molecular features. There is increasing evidence that genetic factors may predispose to DNA methylation. This can result in familial clustering of MSI-H CRC in which the underlying mechanism is methylation of hMLH1 rather than germline mutation. Morphological features can assist is distinguishing such families from bona fide HNPCC families which they closely mimic.

Pathogenesis of colorectal cancer

It is frequently stated that all but a few colorectal cancers arise in adenomatous polyps, in turn initiated by APC mutation. Moderation of this view is now required. The proportion of colorectal cancers that arises in a polypoid adenoma is likely to be around 70% [39,61]. The pre-eminence of the adenoma-carcinoma model has been influenced by two factors: (1) the need to avoid overtreatment of innocent lesions, and (2) the absence of a convincing alternative mechanism. The latter position has changed in recent years. Collectively, the alternative pathways may account for the pathogenesis of up to 30% of colorectal cancers. The alternative pathways are difficult to observe in clinical practice because the precursors may be either inconspicuous or show rapid evolution following the establishment of genetic instability. As a concept, the polyp-cancer sequence is entrenched in both specialized and student texts. This is unfortunate, because progress in prevention and early cancer detection will be delayed by the failure to adopt a critical and nondogmatic approach to the pathogenesis of colorectal cancer. The advent of DNA chip technology will catalyze the development of revised paradigms. Specifically, modern genomics will allow polyps and cancers to be grouped within pathogenic pathways on the basis of shared gene expression profiles. The era of molecular medicine has dawned for colorectal cancer.

Altered mucin expression in the gastrointestinal tract: a review

Early studies of changes in mucin expression in disorders of the gastrointestinal tract focused on alterations in the carbohydrate chain. This review briefly considers the various mechanisms by which such alterations may come about: (a) normal variation, (b) sialic acid alterations, (c) defective assembly of carbohydrate side-chains, (d) changed expression of core proteins and (e) epithelial metaplasia. The availability of monoclonal antibodies to mucin core proteins adds a new dimension to mucin histochemistry. It is now possible to offer explanations for traditional mucin histochemical findings on the basis of lineage-specific patterns of mucin core protein expression. Changes in core protein expression are described in inflammatory, metaplastic and neoplastic disorders of the gastrointestinal tract. The possibility that mucin change could be important in the aetiology of some diseases such as ulcerative colitis and H. pylori gastritis is considered. It is more probable, however, that changes in mucin expression are secondary to reprogramming of cellular differentiation and altered cell turnover. As such they may serve as markers to explain pathogenesis and provide novel diagnostic and prognostic information.