Helicobacter pylori HP(2-20) induces eosinophil activation and accumulation in superficial gastric mucosa and stimulates VEGF-alpha and TGF-beta release by interacting with formyl-peptide receptors.

Eosinophils participate in the immune response against Helicobacter pylori, but little is known about their role in the gastritis associated to the infection. We recently demonstrated that the Hp(2-20) peptide derived from H. pylori accelerates wound healing of gastric mucosa by interacting with N-formyl peptide receptors (FPRs) expressed on gastric epithelial cells. The aim of the present study was to investigate whether eosinophils play a role in the repair of gastric mucosa tissue during H. pylori infection. Immuno-histochemistry and transmission electron microscopy were used to detect eosinophils in gastric mucosal biopsies. Eosinophil re-distribution occurred in the gastric mucosa of H. pylori-infected patients: their density did not change in the deep mucosal layer, whereas it increased in the superficial lamina propria just below the foveolar epithelium; eosinophils entered the epithelium itself as well as the lumen of foveolae located close to the area harboring bacteria, which in turn were also engulfed by eosinophils. The H. pylori-derived peptide Hp(2-20) stimulated eosinophil migration through the engagement of FPR2 and FPR3, and also induced production of VEGF-A and TGF-beta, two key mediators of tissue remodelling. We also demonstrate that Hp(2-20) in vivo induced eosinophil infiltration in rat gastric mucosa after injury brought about by indomethacin. This study suggests that eosinophil infiltrate could modulate the capacity of gastric mucosa to maintain or recover its integrity thereby shedding light on the role of eosinophils in H. pylori infection.

TNM staging of neoplasms of the endocrine pancreas: results from a large international cohort study.

BACKGROUND: Both the European Neuroendocrine Tumor Society (ENETS) and the International Union for Cancer Control/American Joint Cancer Committee/World Health Organization (UICC/AJCC/WHO) have proposed TNM staging systems for pancreatic neuroendocrine neoplasms. This study aims to identify the most accurate and useful TNM system for pancreatic neuroendocrine neoplasms. METHODS: The study included 1072 patients who had undergone previous surgery for their cancer and for which at least 2 years of follow-up from 1990 to 2007 was available. Data on 28 variables were collected, and the performance of the two TNM staging systems was compared by Cox regression analysis and multivariable analyses. All statistical tests were two-sided. RESULTS: Differences in distribution of sex and age were observed for the ENETS TNM staging system. At Cox regression analysis, only the ENETS TNM staging system perfectly allocated patients into four statistically significantly different and equally populated risk groups (with stage I as the reference; stage II hazard ratio [HR] of death = 16.23, 95% confidence interval [CI] = 2.14 to 123, P = .007; stage III HR of death = 51.81, 95% CI = 7.11 to 377, P < .001; and stage IV HR of death = 160, 95% CI = 22.30 to 1143, P < .001). However, the UICC/AJCC/WHO 2010 TNM staging system compressed the disease into three differently populated classes, with most patients in stage I, and with the patients being equally distributed into stages II-III (statistically similar) and IV (with stage I as the reference; stage II HR of death = 9.57, 95% CI = 4.62 to 19.88, P < .001; stage III HR of death = 9.32, 95% CI = 3.69 to 23.53, P = .94; and stage IV HR of death = 30.84, 95% CI = 15.62 to 60.87, P < .001). Multivariable modeling indicated curative surgery, TNM staging, and grading were effective predictors of death, and grading was the second most effective independent predictor of survival in the absence of staging information. Though both TNM staging systems were independent predictors of survival, the UICC/AJCC/WHO 2010 TNM stages showed very large 95% confidence intervals for each stage, indicating an inaccurate predictive ability. CONCLUSION: Our data suggest the ENETS TNM staging system is superior to the UICC/AJCC/WHO 2010 TNM staging system and supports its use in clinical practice.

Gastroenteropancreatic (neuro)endocrine neoplasms: the histology report.

Based on the year 2000 World Health Organization (WHO) classification and the European Neuroendocrine Tumor Society (ENETS) grading and staging proposals, we here define the minimal guidelines for pathology reporting of (neuro)endocrine neoplasms. The macroscopical description is recommended according to standard procedures and the microscopical description according to recognized architectural and cytological features for endocrine lesions. Minimal diagnostic immunohistochemistry entails the use of chromogranin A, synaptophysin and Ki67. Other potentially useful tests are those for CD56 N-CAM, PGP 9.5 and hormones for diagnosis, the somatostatin receptor subtype 2 for potential radiodiagnostics and therapy, and transcription factors like TTF1 and CDX2, for site of origin. Grading definition is always mandatory as well as TNM staging for surgical specimens.

Prevalence of double pituitary adenomas in a surgical series: Clinical, histological and genetic features.

BACKGROUND: The term double pituitary adenomas (DPA) is usually referred to those rare lesions showing two distinct cellular components. Genetic background may sustain the proliferation of more than one cell at the same time but no information is available on the presence of aip mutations in these patients. AIM: We report the prevalence and the endocrinological, neuroradiological, histopathological and genetic features of DPA detected in a large surgical series. The contribution of pituitary transcription factor immunostains in DPA was also evaluated. SUBJECTS AND METHODS: One-hundred-forty-four patients undergoing surgery for tumors of the sellar region were evaluated. Histopathology, immunohistochemistry and the mutational analysis for the entire coding region of the AIP and MEN1 genes were performed. RESULTS: One-hundred-seventeen patients out of 144 had a pituitary adenoma. DPA was found in 3 (2.6%) out of 117 patients with pituitary adenoma. Immunohistochemistry and transcription factors analysis demonstrated two not yet described histotype associations in DPA. The coexistence of somatotroph-lactotroph and silent mammosomatotroph histotype in 1 case and the coexistence of sparsely granulated lactotroph and null cell adenomas in the remaining two cases were first identified. Sequencing data for the coding region of the aip and the menin gene resulted in wild type sequences in all patients with DPA. CONCLUSIONS: The prevalence of DPA observed in our unselected surgical series is not negligible (2.6%). Furthermore, the evaluation of the treatment outcome would suggest that the clinical management of DPAs requires a careful diagnostic approach and follow- up.

Silent familial isolated pituitary adenomas: histopathological and clinical case report.

Familial isolated pituitary adenoma (FIPA) is a rare condition independent of Carney Complex or MEN1. An international multicenter study recently described 28 nonfunctioning pituitary adenomas in 26 families with only two homogeneous nonsecreting phenotype families consistent of silent GH and silent gonadotroph adenomas, respectively. We present the clinical, genetic, and morphological analysis of two silent pituitary adenomas occurring in a man and his daughter, and discuss the differential diagnosis associated with their histological, immunohistochemical, and ultrastructural features. The patients developed invasive nonsecreting macroadenomas manifesting only with compressive symptoms. Genetic analysis in the father showed no MEN-1 germ-line mutation. Tissue samples obtained after paraseptal trans-sphenoidal surgery were studied by immunohistochemistry for adenohypophyseal hormones, low molecular weight cytokeratins (CAM 5.2), proliferation markers, and anterior pituitary transcription factors (Pit-1 and SF-1) and by electron microscopy for secretory granules. The clinical, histological, and immunohistochemical features of the lesions posed a differential diagnosis between a null cell adenoma and a silent corticotroph adenoma (Type II); on the basis of immunohistochemical stains for cytokeratin and adenohypophysis cell lineage markers, tumor behavior and ultrastructural studies we concluded for the second. The reported cases represent an as yet undescribed example of homogeneous family with silent corticotroph adenomas (Type II). Our observations support the trend for more aggressive behavior in nonsecreting FIPAs as compared with sporadic adenomas.

[Guidelines and minimal diagnostic criteria for the histological diagnosis of endocrine tumors of the gastroenteropancreatic type]. / Linee guida e criteri diagnostici minimi per la diagnosi istologica dei tumori endocrini del tratto gastroenteropancreatico.

The endocrine tumors of the pancreas and the gastrointestinal tract may be of difficult interpretation. The recent histopathological classification of the endocrine tumors by the World Health Organization (W.H.O.) introduced new criteria for their interpretation, classification and diagnosis. The present paper aims at defining simple guidelines for the practical, routine approach to the histopathological diagnosis of the endocrine tumors of the digestive system according to the new W.H.O. criteria.

Gastric mucosal atrophy: interobserver consistency using new criteria for classification and grading.

BACKGROUND AND AIMS: Considerable difficulties persist amongst pathologists in agreeing on the presence and severity of gastric atrophy. An international group of pathologists pursued the following aims: (i) to generate an acceptable definition and a simple reproducible classification of gastric atrophy; and (ii) to develop guidelines for the recognition of atrophy useful for increasing agreement among observers. METHODS: After redefining atrophy as the 'loss of appropriate glands' and examining histological samples from different gastric compartments, three categories were identified: (i) negative; (ii) indefinite; (iii) atrophy, with and without intestinalization. Atrophy was graded on a three-level scale. Interobserver reproducibility of the classification was tested by kappa statistics (general and weighted) in a series of 48 cases. RESULTS: The medians of the general agreement and weighted kappa values were 0.78 and 0.73, respectively. The weighted kappa coefficients, obtained by cross-tabulating the evaluation of each pathologist against all others, were, with only one exception, > 0.4 (moderate to excellent agreement). CONCLUSIONS: By using the definition of atrophy as the loss of appropriate glands and distinguishing the two main morphological entities of metaplastic and non-metaplastic types, a high level of agreement was achieved by a group of gastrointestinal pathologists trained in different cultural contexts.

Loss of heterozygosity at 18q21 region in gastric cancer involves a number of cancer-related genes and correlates with stage and histology, but lacks independent prognostic value.

Several studies support a role of 18q21 LOH, involving the DCC locus, in colorectal cancer progression; however, its contribution to the natural history of gastric cancer is less clear. Recently, a number of cancer-related genes have been mapped in the 18q21 region, either centromeric or telomeric to DCC. This study searched for 18q21 LOH in 161 gastric cancers representative of all tumour stages and main histological types. To this purpose, seven highly polymorphic markers were used flanking the 18q21 band and spanning the entire region. Thirty-four out of 147 (23.1%) informative cases showed LOH. In 27 of 34 cases (79%), LOH involved all the informative loci. The remaining seven cases showed LOH at more telomeric sites and retained heterozygosity at more centromeric markers, mostly those proximal to the DCC gene. A strong correlation between 18q21 LOH and level of gastric wall invasion, lymph node metastases, or stage was found in cohesive (glandular+solid) and mixed tumours, but not in diffuse cancers. Cox univariate and multivariate analysis showed that invasion level, lymph node metastases, distant metastases, TNM stage, and histology were effective predictors of survival, whereas 18q21 LOH did not show predictive power. The simultaneous deletion of a variety of cancer-related genes with different and even opposite roles might explain why, apparently, 18q21 LOH does not per se contribute significantly to the natural history of gastric cancer, despite strong correlation with stage.

Morphometric assessment of gastric antral atrophy: comparison with visual evaluation.

AIMS: As part of a multinational effort to reach a consensus in the definition and evaluation of atrophic gastritis, we applied morphometric techniques to 22 antral biopsy specimens examined visually by 12 experienced gastrointestinal pathologists. METHODS AND RESULTS: Atrophy was defined as loss of glands. Each pathologist graded atrophy with both non-standardized and standardized approaches. Discriminant function analyses of morphometric measurements were conducted to validate and grade atrophy. Kappa statistics were used to compare the performance of each pathologist against the group mode and against the discriminant functions' grading of atrophy. Three morphometric indexes showed significant differences among categories of atrophy utilizing non-standardized as well as standardized visual atrophy grades: (i) the ratio of glandular length to total mucosal thickness; (ii) the proportion of the secretory compartment area occupied by glands; and (iii) the number of glandular cross sections per 40x microscopic field. The discriminant function analyses verified all cases classified visually as either non-atrophic, or moderately/severely atrophic; it verified as mildly atrophic 40% of the cases classified visually as mildly atrophic; and classified the remaining 60% as moderately or severely atrophic. The kappa statistics were good or excellent for the majority of pathologists. CONCLUSIONS: The evaluation of antral atrophy, simply defined as loss of glands, can be reliable and reproducible. The visual grading of atrophy as absent, moderate and severe is entirely consistent with objective morphometric observations.

The role of histological investigation in prognostic evaluation of advanced gastric cancer. Analysis of histological structure and molecular changes compared with invasive pattern and stage.

The relative contribution of tumour histology or molecular changes, compared with invasion pattern or stage, to prognostic assessment of gastric cancer was investigated in a series of 185 advanced (T2 to T4, stage IB to IV) cancers that had undergone intentionally curative surgery at Varese General Hospital. Survival analysis of the histological types considered in commonly used classifications, such as Lauren, Kubo, the World Health Organization (WHO) and related classifications, allowed separation of a small high-grade (Hg, 12 cases) group of adenosquamous, anaplastic and small cell endocrine carcinomas from a large cohesive group (C, 86 glandular or solid cancers) and from another large (87 cases) group of tumours with dissociated cells [29 diffuse (D) and 58 mixed (M) tumours]. Univariate and multivariate analysis showed the independent prognostic value of this C/M+D/Hg classification approach, which proved superior to other classifications and to cell dissociation at the growing front or angio, lympho and neuro-invasion. Expression of sialyl Lewis(c), the DUPAN-2 antigen, proved to be an independent predictor of worse survival among tumours beyond stage I, showing an exclusively or predominantly cohesive structure. Microsatellite instability (MSI) predicted favourable survival in purely cohesive tumours of intermediate (II) stage, especially of solid/medullary and lymphoid stroma/lympho-epithelioma-like structure, among which two distinct tumour subsets were characterised, one MSI-positive and the other Epstein-Barr virus positive. T2NOM0 (stage IB) tumours showed mostly favourable survival independently from histological type, invasive pattern, DUPAN-2 or MSI status. It is concluded that an appropriate histological evaluation, coupled with sialylated glycoproteins histochemistry and, for stage-II tumours, MSI tests may contribute significantly to prognostic assessment of tumours beyond stage I. However, the stage itself, with special reference to lymph-node metastases and invasion level beyond subserosa, remains the most important prognostic clue for gastric cancer.

Effects of very long (up to 10 years) proton pump blockade on human gastric mucosa.

BACKGROUND: Long-term use of proton pump inhibitors (PPI) has been reported to worsen oxyntic mucosa gastritis and the resulting gland atrophy has been considered a potential risk factor for neoplastic changes in the gastric mucosa. AIMS: The present study examines the effect of extended continuous PPI treatment for up to 10 years on the exocrine and endocrine stomach of patients with acid-related diseases of the upper GI tract. METHODS: Biopsies from the antral and oxyntic mucosa taken at regular time intervals were examined for gastritis, atrophy, intestinal metaplasia, Helicobacter pylori and argyrophil cells and correlated to serum gastrin levels. RESULTS: A general amelioration of antral gastritis without relevant changes of atrophy or intestinal metaplasia, contrasted with the worsening of gastritis and gland atrophy seen in the oxyntic mucosa of reflux esophagitis (but not gastric or duodenal ulcer) patients in the presence of H. pylori infection. In association with PPI- induced hypergastrinemia, argyrophil cell hyperplasia (but not dysplasia or neoplasia) developed in the oxyntic mucosa. CONCLUSION: The present results outline the milder pretreatment pattern and higher proneness to PPI-related, H. pylori-restricted worsening of oxyntic mucosa gastritis in reflux esophagitis compared to gastric ulcer or duodenal ulcer patients. In addition, they confirm a substantial safety of long-term PPI therapy as concerns neoplastic changes in the exocrine and endocrine human stomach.

The N-terminal 34 kDa fragment of Helicobacter pylori vacuolating cytotoxin targets mitochondria and induces cytochrome c release.

The pathogenic bacterium Helicobacter pylori produces the cytotoxin VacA, which is implicated in the genesis of gastric epithelial lesions. By transfect ing HEp-2 cells with DNAs encoding either the N-terminal (p34) or the C-terminal (p58) fragment of VacA, p34 was found localized specifically to mitochondria, whereas p58 was cytosolic. Incubated in vitro with purified mitochondria, VacA and p34 but not p58 translocated into the mitochondria. Microinjection of DNAs encoding VacA-GFP and p34-GFP, but not GFP-VacA or GFP-p34, induced cell death by apoptosis. Transient transfection of HeLa cells with p34-GFP or VacA-GFP induced the release of cytochrome c from mitochondria and activated the executioner caspase 3, as determined by the cleavage of poly(ADP-ribose) polymerase (PARP). PARP cleavage was antagonized specifically by co-transfection of DNA encoding Bcl-2, known to block mitochondria-dependent apoptotic signals. The relevance of these observations to the in vivo mechanism of VacA action was supported by the fact that purified activated VacA applied externally to cells induced cytochrome c release into the cytosol.

High cell sensitivity to Helicobacter pylori VacA toxin depends on a GPI-anchored protein and is not blocked by inhibition of the clathrin-mediated pathway of endocytosis.

Helicobacter pylori vacuolating toxin (VacA) causes vacuolation in a variety of cultured cell lines, sensitivity to VacA differing greatly, however, among the different cell types. We found that the high sensitivity of HEp-2 cells to VacA was impaired by treating the cells with phosphatidylinositol-specific phospholipase C (PI-PLC) which removes glycosylphosphatidylinositol (GPI)-anchored proteins from the cell surface. Incubation of cells with a cholesterol-sequestering agent, that impairs both structure and function of sphingolipid-cholesterol-rich membrane microdomains ("lipid rafts"), also impaired VacA-induced cell vacuolation. Overexpression into HEp-2 cells of proteins inhibiting clathrin-dependent endocytosis (i.e., a dominant-negative mutant of Eps15, the five tandem Src-homology-3 domains of intersectin, and the K44A dominant-negative mutant of dynamin II) did not affect vacuolation induced by VacA. Nevertheless, F-actin depolymerization, known to block the different types of endocytic mechanisms, strongly impaired VacA vacuolating activity. Taken together, our data suggest that the high cell sensitivity to VacA depends on the presence of one or several GPI-anchored protein(s), intact membrane lipid rafts, and an uptake mechanism via a clathrin-independent endocytic pathway.

Gastric endocrine cells: types, function and growth.

The history of gastric endocrine cells identification and functional characterization is briefly outlined. An up to date classification of such cells is given. Present status of histopathological, histochemical, ultrastructural and molecular investigations on gastric endocrine hyperplasia and neoplasia is summarized and briefly discussed.

Introduction to a revised clinicopathological classification of neuroendocrine tumors of the gastroenteropancreatic tract.

A revised clinicopathological classification of neuroendocrine tumors of the gastroenteropancreatic tract has been recently developed under the auspices of the World Health Organization (WHO) according to advances in the field of tumor biology. Here the classification is briefly outlined and discussed together with the guidelines for a correct approach to the histopathological diagnosis of neuroendocrine tumors and the interpretation of the classification schemes covering clinical (hyperfunctional syndromes included), pathological and biological patterns, with special emphasis on tumor prognosis.

The Vienna classification of gastrointestinal epithelial neoplasia.

BACKGROUND: Use of the conventional Western and Japanese classification systems of gastrointestinal epithelial neoplasia results in large differences among pathologists in the diagnosis of oesophageal, gastric, and colorectal neoplastic lesions. AIM: To develop common worldwide terminology for gastrointestinal epithelial neoplasia. METHODS: Thirty one pathologists from 12 countries reviewed 35 gastric, 20 colorectal, and 21 oesophageal biopsy and resection specimens. The extent of diagnostic agreement between those with Western and Japanese viewpoints was assessed by kappa statistics. The pathologists met in Vienna to discuss the results and to develop a new consensus terminology. RESULTS: The large differences between the conventional Western and Japanese diagnoses were confirmed (percentage of specimens for which there was agreement and kappa values: 37% and 0.16 for gastric; 45% and 0.27 for colorectal; and 14% and 0.01 for oesophageal lesions). There was much better agreement among pathologists (71% and 0.55 for gastric; 65% and 0.47 for colorectal; and 62% and 0.31 for oesophageal lesions) when the original assessments of the specimens were regrouped into the categories of the proposed Vienna classification of gastrointestinal epithelial neoplasia: (1) negative for neoplasia/dysplasia, (2) indefinite for neoplasia/dysplasia, (3) non-invasive low grade neoplasia (low grade adenoma/dysplasia), (4) non-invasive high grade neoplasia (high grade adenoma/dysplasia, non-invasive carcinoma and suspicion of invasive carcinoma), and (5) invasive neoplasia (intramucosal carcinoma, submucosal carcinoma or beyond). CONCLUSION: The differences between Western and Japanese pathologists in the diagnostic classification of gastrointestinal epithelial neoplastic lesions can be resolved largely by adopting the proposed terminology, which is based on cytological and architectural severity and invasion status.

Review article: potential gastrointestinal effects of long-term acid suppression with proton pump inhibitors.

This review examines the evidence for the development of adverse effects due to prolonged gastric acid suppression with proton pump inhibitors. Potential areas of concern regarding long-term proton pump inhibitor use have included: carcinoid formation; development of gastric adenocarcinoma (especially in patients with Helicobacter pylori infection); bacterial overgrowth; enteric infections; and malabsorption of fat, minerals, and vitamins. Prolonged proton pump inhibitor use may lead to enterochromaffin-like cell hyperplasia, but has not been demonstrated to increase the risk of carcinoid formation. Long-term proton pump inhibitor treatment has not been documented to hasten the development or the progression of atrophic gastritis to intestinal metaplasia and gastric cancer, although long-term studies are required to allow definitive conclusions. At present, we do not recommend that patients be tested routinely for H. pylori infection when using proton pump inhibitors for prolonged periods. Gastric bacterial overgrowth does increase with acid suppression, but important clinical sequelae, such a higher rate of gastric adenocarcinoma, have not been seen. The risk of enteric infection may increase with acid suppression, although this does not seem to be a common clinical problem with prolonged proton pump inhibitor use. The absorption of fats and minerals does not appear to be significantly impaired with chronic acid suppression. However, vitamin B12 concentration may be decreased when gastric acid is markedly suppressed for prolonged periods (e.g. Zolllinger-Ellison syndrome), and vitamin B12 levels should probably be assessed in patients taking high-dose proton pump inhibitors for many years. Thus, current evidence suggests that prolonged gastric acid suppression with proton pump inhibitors rarely, if ever, produces adverse events. Nevertheless, continued follow-up of patients taking proton pump inhibitors for extended periods will provide greater experience regarding the potential gastrointestinal adverse effects of long-term acid suppression.

Altered intercellular glycoconjugates and dilated intercellular spaces of esophageal epithelium in reflux disease.

BACKGROUND AND AIMS: The usefulness of histological diagnosis of gastroesophageal reflux disease (GERD) is limited by poor specificity or sensitivity of available diagnostic tools. Recently, ultrastructural morphometry showed interstitial space dilation (ISD) to be a reliable sign of reflux disease. Aims of this study were to (a) search for a light microscopy equivalent of ISD, (b) test its diagnostic value, and (c) look for a possible role of intercellular glycoconjugates in its genesis. METHODS: Esophageal grasp biopsies were taken during endoscopy, 2-3 cm and 6-7 cm above the squamocolumnar junction, from patients under investigation for GERD symptoms. The biopsies were fixed in aldehyde solutions and embedded in resin for electron microscopy or in paraffin for routine histology, and the glycoconjugates underwent immunohistochemistry using 3-fucosyl-N-acetylactosamine antibodies. RESULTS: Irregular intercellular space dilation was detected in the basal and prickle layers using both light and electron microscopy. Hematoxylin-eosin preparations showed ISD in 20 of 22 (90%) erosive esophagitis cases, 30 of 44 (68%) endoscopy negative GERD cases, and 1 of 12 (8%) controls, with good interobserver (K = 0.75) and bioptic site reproducibility. ISD correlated with loss or rearrangement of intercellular glycoconjugates of the overlying layers and with granulocyte (eosinophil and/or neutrophil) infiltration. CONCLUSIONS: Light microscopy ISD is a suitable index of GERD. Alterations of intercellular glycoconjugates are likely to have a role in the genesis of ISD and GERD.

Vesicular monoamine transporter 2 as a marker of gastric enterochromaffin-like cell tumors.

The vesicular monoamine transporter 2 (VMAT2) facilitates the ATP-dependent accumulation of biogenic amine inside the secretory granules of endocrine cells and neurons and was demonstrated in the histamine-producing enterochromaffin-like (ECL) cells of the stomach. In the present investigation, VMAT2 immunohistochemistry was tested in 85 endocrine tumors, of which 60 were well differentiated gastrointestinal and pancreatic growths, 5 poorly differentiated (neuro)endocrine carcinomas (PDEC) and 1 mixed PDEC/ECL cell carcinoma of the stomach, 12 pheochromocytomas/paragangliomas, 3 adrenocortical lesions, 2 parathyroid and 2 lung neuroendocrine tumors. Extensive and intense VMAT2 immunoreactivity was observed in 16 of 16 gastric ECL cell tumors, 6 of 6 adrenal pheochromocytomas, 2 of 2 chromaffin paragangliomas and in 3 of the 4 carotid body paragangliomas investigated. Rare VMAT2-positive cells were observed in 12 of 21 intestinal enterochromaffin (EC) cell tumors, in 9 of 11 pancreatic neuroendocrine tumors, and in the mixed PDEC/ ECL cell carcinoma of the stomach (differentiated cells only). No VMAT2 immunoreactivity was observed in five gastrin, four somatostatin and three enteroglucagon/peptideYY tumors of the gastrointestinal tract, in six gastric PDECs, in three adrenocortical growths, and two parathyroid and two lung neuroendocrine tumors. These data support VMAT2 immunohistochemistry as being a useful tool for the diagnosis of gastric ECL cell tumors, separating them from all other endocrine tumors arising in the gastroduodenal area i.e., gastrin, somatostatin, EC cell and PDEC tumors, all of which proved essentially negative.