Pólipos de glândulas fúndicas: a histologia pode ser utilizada para prever uso de inibidores de bomba de próton? / Gastric fundic gland polyps: can histology be useful to predict proton pump inhibitors use?

ABSTRACT BACKGROUND: Fundic gland polyps allegedly increased in frequency in recent decades, and had attracted great attention due to possible association with prolonged proton pump inhibitor therapy. Prolonged use of this drug could cause parietal cell hyperplasia, obstruction of glandular lumen and cystic dilation of the gland. OBJECTIVE: This study aims to analyze clinical and pathological features of fundic gland polyps in patients with and without proton pump inhibitor therapy in a selected population from Brazil. METHODS: It was selected a sample of 101 Brazilian patients (78 females and 23 males), from a five years retrospective search of the files from a private pathology laboratory. The patients had an average age of 57 years and we included patients with a histological diagnosis of fundic gland polyp. The clinical data were obtained from their files and all histological slides were reviewed and examined with hematoxylin and eosin (HE) and Giemsa. RESULTS: Information about the use or non-use of proton pump inhibitors (PPI) was obtained in 84 patient files. In 17 cases we could not determine if PPI were used or not. Among those in which the information was available, a positive history of anti-acid therapy was observed in 63 (75.0%) patients. Parietal cell hypertrophy/hyperplasia and parietal cell protrusions were detected in most slides. Histological findings were identical in PPI users and PPI negative patients. Helicobacter pylori infection was detected in just two samples. Epithelial dysplasia or adenocarcinoma were not observed in our cases. Histopathological analysis of fundic gland polyps could not distinguish between PPI and non-PPI related cases. Parietal cell cytoplasmic protrusions, an alleged marker of prolonged acid suppression therapy, was detected in both groups. CONCLUSION: Histological features could not discriminate anti-acid therapy related fundic glands polyps in our patients.

RESUMO CONTEXTO: Os pólipos das glândulas fúndicas do estômago supostamente aumentaram em frequência nas últimas décadas e atraíram grande atenção devido à possível associação com a terapia prolongada com inibidores da bomba de prótons. O uso prolongado deste fármaco pode causar hiperplasia das células parietais, obstrução do lúmen glandular e dilatação cística da glândula. OBJETIVO: Este estudo tem como objetivo analisar os aspectos clínicos e patológicos dos pólipos das glândulas fúndicas em pacientes com e sem terapia com inibidores da bomba de prótons em uma população selecionada do Brasil. MÉTODOS: Foi selecionada uma amostra de 101 pacientes brasileiros (78 do sexo feminino e 23 do sexo masculino), a partir de uma pesquisa retrospectiva de cinco anos dos arquivos de um laboratório privado de patologia. Os pacientes tinham uma idade média de 57 anos e foram incluídos pacientes com diagnóstico histológico de pólipo das glândulas fúndicas. Os dados clínicos foram obtidos a partir de seus prontuários e todas as lâminas histológicas foram revisadas e examinadas com hematoxilina e eosina (HE) e Giemsa. RESULTADOS: Informações sobre o uso ou não uso de inibidores da bomba de próton (IBP) foram obtidas em 84 prontuários de pacientes. Em 17 casos, não foi possível determinar se o IBP foi usado ou não. Entre aqueles em que a informação estava disponível, observou-se uma história positiva de terapia com IBP em 63 (75,0%) pacientes. A hipertrofia das células parietais/hiperplasia e protrusões das células parietais foram detectadas na maioria das lâminas. Os achados histológicos foram idênticos em usuários de IBP e pacientes não usuários. A infecção por Helicobacter pylori foi detectada em apenas duas amostras. A displasia epitelial ou o adenocarcinoma não foram observados em nossos casos. A análise histopatológica dos pólipos das glândulas fúndicas não pôde distinguir entre os casos IBP e não relacionados ao IBP. As protuberâncias citoplasmáticas das células parietais, um suposto marcador de terapia prolongada de supressão de ácido, foram detectadas em ambos os grupos. CONCLUSÃO: Características histológicas não podem discriminar os pólipos das glândulas fúndicas relacionados à terapia anti-secretora em nossos pacientes.

Doenças imunomediadas em pacientes com doença celíaca e em seus familiares: um estudo comparativo entre idade e sexo / Immune mediated diseases in patients with celiac disease and their relatives: a comparative study of age and sex

ABSTRACT BACKGROUND: Up to 15% of other immune-mediated diseases (IMDs) can occur in patients with CD throughout their lives and are associated with multiple factors, including sex and sex hormone levels. Moreover, sex is associated with differences in clinical presentation, onset, progression, and outcomes of disorders. OBJECTIVE: To investigate the prevalence of IMDs at diagnosis in patients with celiac disease (CD) and their first-degree relatives and to compare the findings between female and male patients of different age. METHODS: A retrospective study including Brazilian patients with CD who visited the same doctor during January 2012 to January 2017 was performed. Demographic and medical history data were collected through self-administered questionnaires and medical charts of the patients. In total, 213 patients were examined at diagnosis: 52 males (mean age, 40.0 years) and 161 females (mean age, 41.4 years). The patients were divided into two groups according to sex and age. RESULTS: IMDs were observed in 60.2% of the female (97/161) and 42.3% of the male patients (22/52; P=0.22). However, the frequency of IMDs was significantly higher in females aged 51-60 years than in males with same age (P=0.0002). Dermatitis herpetiformis (DH) was significantly more prevalent in males (P=0.02), whereas atopy was more prevalent in females (P=0.02). IMDs observed in first-degree relatives were similar to those observed in patients (70.9%; P<0.001), with a higher number observed in female relatives. CONCLUSION: The frequency of IMDs in CD patients was similar in all age groups and both sexes, except women diagnosed with CD after 51 years of age presented with an increased frequency of IMDs compared with males. Dermatitis herpetiformis was more prevalent in males, whereas atopy was more prevalent in females. No difference was observed in the type of IMDs between the first-degree relatives of both sexes.

RESUMO CONTEXTO: Até 15% das outras doenças imunomediadas (DIMs) podem ocorrer em pacientes com doença celíaca ao longo de suas vidas e estão associados a múltiplos fatores, incluindo sexo e níveis de hormônios sexuais. Além disso, o sexo está associado a diferenças na apresentação, início, progressão e desfecho das doenças. OBJETIVO: Investigar a prevalência de DIMs ao diagnóstico de doença celíaca e em seus familiares de primeiro grau e comparar os resultados entre sexo feminino e masculino em diferentes idades. MÉTODOS: Estudo retrospectivo incluindo pacientes brasileiros com diagnóstico de doença celíaca que realizaram acompanhamento com o mesmo médico no período de janeiro 2012 a janeiro de 2017. Dados demográficos e histórico médico foram coletados através de um questionário auto administrado e prontuários médicos dos pacientes envolvidos. No total, 213 pacientes eram portadores de doença celíaca, dos quais 52 do sexo masculino (idade média 40,0 anos) e 161 do sexo feminino (idade média 41,4 anos). Os pacientes foram divididos em dois grupos de acordo com o sexo e idade. RESULTADOS: DIMs foram observadas em 60,2% das pacientes femininas (97/161) e 42,4% dos pacientes masculinos (22/52; P=0,22). Entretanto, a frequência de DIMs foi significantemente maior em pacientes do sexo feminino com idade entre 51-60 anos que em pacientes masculinos da mesma idade (P=0,0002). Dermatite herpetiforme apresentou maior prevalência no sexo masculino (P=0,02), enquanto atopia obteve maior prevalência nas pacientes do sexo feminino (P=0,02). DIMs observadas em familiares de primeiro grau foram similares as encontradas nos pacientes (70,9%; P<0,001), com um maior número observado em familiares femininos. CONCLUSÃO: A frequência de DIMs em pacientes com doença celíaca foi similar nos grupos etários e ambos sexos, exceto as mulheres com diagnóstico de doença celíaca após a idade de 51 anos, as quais apresentaram um aumento na frequência de DIMs em comparação com os pacientes do sexo masculino. Dermatite herpetiforme apresentou maior prevalência em pacientes do sexo masculino, enquanto que atopia foi mais prevalente no sexo feminino. Em relação ao sexo, não foi observada diferença no tipo de DIMs observada entre os familiares de primeiro grau.

Análise qualitativa das alterações anatomopatológicas na mucosa gástrica decorrentes da terapêutica prolongada com inibidores da bomba de prótons: estudos experimentais x estudos clínicos / Qualitative analysis of anatomopathological changes of gastric mucosa due to long term therapy with proton pump inhibitors: experimental studies x clinical studies

INTRODUÇÃO: Há algumas décadas o uso prolongado de inibidores de bomba de prótons tem tido ampla aplicação no tratamento de doenças gastrointestinais. Desde então, entretanto, vários estudos têm alertado para o possível desenvolvimento de alterações anatomopatológicas da mucosa gástrica, decorrentes do uso prolongado desta modalidade terapêutica. Estudos clínicos e experimentais recentes sugerem que estas alterações teriam relação com o desenvolvimento não só de lesões pré-neoplásicas mas, também, de tumores gástricos. OBJETIVO: Apresentar uma análise qualitativa das alterações antomopatológicas da mucosa gástrica decorrentes do uso prolongado dos inibidores da bomba de prótons. MÉTODOS: Foram utilizados os descritores inibidores da bomba de prótons, lesões pré-neoplásicas e neoplasias gástricas para revisão não sistemática narrativa da literatura, com base nas plataformas Medline, Lillacs e Scielo. Foram selecionados 12 artigos, dentre estudos clínicos (9) e experimentais (3), para análise qualitativa dos resultados apresentados. RESULTADOS: A supressão ácida gástrica por altas doses de inibidores de bomba de prótons induz hipergastrinemia e o consequente aparecimento de tumores neuroendócrinos, em modelos animais. As alterações morfológicas encontradas nestes estudos experimentais foram: hiperplasia de células enterocromafins like, tumor neuroendócrino, atrofia, metaplasia e adenocarcinoma. Os estudos em humanos, entretanto, apesar de demostrarem hiperplasia de células enterocromafins like, tumores neuroendócrino e atrofia gástrica, não identificaram metaplasia gástrica ou adenocarcinoma. CONCLUSÃO: Apesar de não ser possível afirmar que o tratamento prolongado com inibidores de bomba de prótons induza ao aparecimento ou acelere o desenvolvimento do câncer gástrico, em humanos, vários autores sugeriram que a administração prolongada poderia promover o desenvolvimento do câncer gástrico. Dessa forma, as evidências demonstradas no modelo animal, bem como o grande número de pacientes que fazem ou que farão tratamento prolongado com esta classe de medicamentos, alertam para necessidade de seu uso mais criterioso, bem como, justificam a manutenção desta importante linha de pesquisa.

INTRODUCTION: For a few decades the long-term use of proton pump inhibitors has had wide application in the treatment of several gastrointestinal diseases. Since then, however, several studies have called attention to the possible development of anatomical and pathological changes of gastric mucosa, resulting from the long term use of this therapeutic modality. Recent experimental and clinical studies suggest that these changes have connection not only to the development of precancerous lesions, but also of gastric tumors. OBJECTIVE: To present a qualitative analysis of anatomical and pathological changes of gastric mucosa resulting from the long-term use of proton pump inhibitors. METHOD: The headings used were: proton pump inhibitors, precancerous lesions and gastric neoplasms for a non systematic review of the literature, based on Medline, Lillacs and Scielo. Twelve articles were selected from clinical (9) and experimental (3) studies, for qualitative analysis of the results. RESULTS: The gastric acid suppression by high doses of proton pump inhibitors induces hypergastrinemia and the consequent emergence of neuroendocrine tumors in animal models. Morphological changes most often found in these experimental studies were: enterochromaffin-like cell hyperplasia, neuroendocrine tumor, atrophy, metaplasia and adenocarcinoma. In the studies in humans, however, despite enterochromaffin-like cell hyperplasia, the other effects, neuroendocrine tumor and gastric atrophy, gastric metaplasia and or adenocarcinoma, were not identified. CONCLUSION: Although it is not possible to say that the long-term treatment with proton pump inhibitors induces the appearance or accelerates the development of gastric cancer in humans, several authors have suggested that prolonged administration of this drug could provoke the development of gastric cancer. Thus, the evidence demonstrated in the animal model as well as the large number of patients who do or will do a long-term treatment with proton pump inhibitors, justifies the maintenance of this important line of research.

Linfoma no Hodgkin gástrico asociado a intoxicación por metales pesados / Gastric non-Hodgkin lymphoma associated with heavy metal exposures

El Linfoma no Hodgkin (LNH) extraganglionar es una neoplasia maligna que corresponde al 40% de los casos de LNH, siendo el tracto gastrointestintal (TGI) la localización más común. Dentro del TGI es el estómago el órgano más afectado (60%). Presentamos el caso de un hombre de 52 años trabajador en empresa minera por más de 10 años, el cual es derivado al Servicio de Gastroenterología por presentar un cuadro de epigastralgia, náuseas y baja de peso. La endoscopía digestiva mostró una lesión ulcerada en cuerpo gástrico a la cual se le tomaron múltiples biopsias. El estudio histológico y el posterior análisis inmunohistoquímico permitieron realizar el diagnóstico de LNH B difuso de células grandes. Asimismo, el paciente presentó compromiso de múltiples órganos en relación a exposición crónica de metales pesados, lo cual fue comprobado en el mineralograma, siendo las de mayor concentración el uranio, talio, arsénico, plomo y mercurio. En la literatura se ha descrito la asociación de exposición laboral crónica a Uranio y Arsénico con la presentación de LNH de compromiso gastrointestinal. Por tal motivo, el compromiso gástrico no se puede considerar como un daño aislado, sino más bien parte del compromiso sistémico asociado a concentraciones elevadas de metales. La minería constituye el principal motor de ingresos económicos para el Perú, sin embargo, no existen reportes hasta la fecha de la asociación de LNH de compromiso gastrointestinal en relación a exposición laboral a metales pesados.

Primary extranodal Non-Hodgkin lymphoma (NHL) is a non epithelial tumours that accounts for 40% of cases of NHL. Spread of nodal lymphomas to the gastrointestinal tract (GIT) is the most common location. Within the GIT is the stomach the most affected organ (60%). We report the case of 52-year- old man, mining company worker for over 10 years, which is derived to the Service of Gastroenterology with history of epigastric pain, nausea, vomiting and weight loss. Upper gastrointestinal endoscopic examination revealed an ulcerated lesion on greater curve of stomach and histopathological examination and subsequent immunohistochemical analysis showed diffuse large B cell gastric NHL. Also, the patient had multiple organ involvement in relation to chronic exposure to heavy metals, which was found in the mineralograma, with the highest concentration of uranium, thallium, arsenic, lead and mercury. The literature has described the association of chronic occupational exposure to uranium and arsenic with NHL presenting gastrointestinal involvement. Therefore, gastric commitment can not be considered as an isolated injury, but rather part of systemic involvement associated with elevated concentrations of metals. Mining is a key driver of income for Peru; however, there are no reports to date of the association of gastrointestinal NHL commitment regarding occupational exposure to heavy metals.

[Study of cyclooxygenase-2 expression in Sprague Dawley rat gastric cancer induced by H. pylori]

Gastric cancer is one of the most common gastrointestinal tumors; the incidence and mortality of gastric cancer are on the increase nowadays. Helicobacter pylori [H.Pylori] causes chronic active gastritis and peptic ulcer disease. Cycloocygenase-2 [COX-2] is the central enzyme in the biosynthetic pathway to prostaglandins. Studies from different laboratories suggested that over-expression of COX-2 was detected in colon and other tumors. To obtain direct evidence concerning this relationship, we investigated the immunohistochemical findings of gastric mucosa using an animal model of gastric cancer induced by H. pylori in sprague dawley rat. The rats were randomly assigned into three groups [n=5]. Those of experimental group2 were given MNU. One week after completion of MNU administration, rats in experimental groups 1 were inoculated with H. pylori three times every other day. Rats in control group [group 3] received neither MNU nor H. pylori. Rats of groups 1, 2, and control group were maintained on standard diets throughout the experiment. Rats were weighed and sacrificed under anesthesia with ether at 20 weeks after infection. One half of the excised stomachs, were fixed in neutral-buffered 10% formalin and were cut into approximately six strips, which were processed by standard methods, embedded in paraffin, sectioned at 6 micro m, and stained with hematoxylin and eosin [H and E] and immunohistochemistry for Cox-2 protein detection. To confirm H. pylori infection, samples [3-mm[2]] of stomach mucosa transferred to appropriate medium and colonies were identified by characteristic Gram's stain morphology, and by urease, catalase, and oxidase activity sample was also placed into the gel of a rapid urease test kit. Data showed a significant decrease of animal body weight in experimental groups compared with control group. Histopathological studies showed severe infiltration of the lamina propria and submucusaal layer by polymorphonuclear and mononuclear cells appeared in the antrum, with an increase in epithelial cell proliferation, and the infiltration of focal oesophageal. Control animals showed no abnormal findings throughout the entire observation period. COX-2 protein was expressed in experimental groups but there were no evidence of cox-2 protein expression in control group. Data showed that the H. pylori caused significant decrease of body weight in experimental group. In addition, histological studies showed evidence of metaplasia in rat stomach. Immunohistochemichas studies showed cox-2 protein expression occurred during early stage of metaplasia induction

A questão do nitrato em alface hidropônica e a saúde humana / The nitrate issue in hydroponic lettuce and the human health

A alface (Lactuca sativa L.) destaca-se como a espécie mais produzida em sistema hidropônico. Nesse tipo de cultivo, a maior parte do nitrogênio é fornecida na forma de nitrato, o que pode acarretar acúmulo deste íon nos vacúolos celulares. O teor de nitrato nas plantas depende de fatores genéticos, da disponibilidade desse nutriente no sistema radicular e de fatores ambientais. Diversos estudos indicam que o consumo de nitrato pode ser nocivo à saúde humana, causando metahemoglobinemia e câncer gástrico. Porém, pesquisas recentes discorrem que não há ligação entre nitrato e as doenças citadas, destacando ainda o papel benéfico do nitrato à saúde humana, como protetor contra gastrenterites. Existem indícios de que a presença de certas vitaminas em vegetais inibe uma possível ação negativa do nitrato. Altas concentrações de nitrato em alface cultivada sob hidroponia em países do norte europeu causaram apreensão da comunidade científica e de consumidores brasileiros. Porém, as pesquisas realizadas no Brasil demonstram que, por haver maior disponibilidade de radiação solar, devido às menores latitudes, os teores de nitrato encontrados em alface produzida em hidroponia são bastante inferiores aos limites máximos preconizados pela união européia, indicando não haver risco à saúde humana.

Lettuce (Lactuca sativa L.) is the main vegetable crop produced hydroponically. In this kind of cropping, the majority of nitrogen is provided as nitrate, which may lead to the accumulation of this ion in cells. Nitrate amount in plants depends upon genetic factors, the availability of this nutrient in roots and environmental factors. Several studies have indicated that the consumption of nitrate may be harmful to human health, causing methaemoglobinaemia and gastric cancer. However, recent studies have proposed that there is no link between nitrate and these diseases, and that nitrate may be even good for human health as a protector against gastroenteritis. Some other studies have indicated that the presence of certain vitamins in plants is likely to inhibit possible negative effects of nitrate. High nitrate concentrations in lettuce grown hydroponically in northern European countries have been a matter of concern to the scientific community and Brazilian consumers. Nevertheless, studies have demonstrated that in Brazil, because of higher solar radiation at low latitudes, nitrate amounts found in lettuce produced hydroponically are much lower than the amounts given by the European community, indicating no risk to human health.

Spontaneous Resolution of Multiple Fundic Gland Polyps after Cessation of Treatment with Omeprazole / 대한소화기학회지

Fundic gland polyps (FGPs) are the most common type of gastric polyps, found primarily in the fundus and body of stomach. Long term use of proton pump inhibitor (PPI) is known to be associated with certain histological changes of the normal gastric mucosa including parietal cell hyperplasia and fundic gland cysts. We experienced a patient who showed spontaneous resolution of multiple FGPs after the cessation of omeprazole. Two years ago, the patient showed only endoscopically confirmed erosive esophagitis without FGPs. Multiple FGPs developed one year after the use of omeprazole and spontaneously disappeared with the cessation of omeprazole.

Azadirachta indica leaf extract modulates initiation phase of murine forestomach tumorigenesis.

The effects of aqueous Azadirachta indica leaf extract (AAILE) on benzo(a)pyrene [B(a)P]-induced forestomach tumorigenesis, B(a)P-DNA adduct formation and certain parameters of carcinogen biotransformation system in mice have been reported earlier from our laboratory. In this study, the effects of AAILE on the enzymes of B(a)P biotransformation, which play crucial role in initiation of chemical carcinogenesis - aryl hydrocarbon hydroxylase (AHH) and uridinediphosphoglucuronosyltransferase (UDP-glucuronosyltransferase) have been evaluated in murine forestomach and liver. In addition, lipid peroxidation (LPO) levels in forestomach as well as liver and the activities of tissue injury marker enzymes - lactate dehydrogenase, aspartate aminotransferase and alkaline phosphatase in the serum have also been evaluated. Oral administration of AAILE (100 mg/kg body wt for 2 weeks) reduces the AHH activity and enhances the UDP-glucuronosyltransferase activity in both the tissues, suggesting its potential in decreasing the activation and increasing the detoxification of carcinogens. The LPO levels decrease upon AAILE treatment in the hepatic tissue, suggesting its antioxidative and hence anti-carcinogenic effects. Non-significant alterations have been observed in tissue injury marker enzymes upon AAILE treatment, suggesting its safety at the given dose. In conclusion, AAILE appears to modulate initiation phase of carcinogenesis and may be suggested as safe and an effective agent for chemoprevention.

Inhibition of N-Methyl N'-nitro-N-nitrosoguanidine (MNNG) induced gastric carcinogenesis by Phyllanthus amarus extract.

Chemopreventive activity of Phyllanthus amarus Schum & Thonn (Euphorbiaceae) extract was studied with regard to N-methyl N'-nitro-N-nitrosoguanidine (MNNG) induced stomach cancer in Wistar rats. Administration of the extract with MNNG significantly reduced the incidence of gastric neoplasms in rats (44%) as well as their numbers. Moreover, elevated levels of enzymes in the stomach were found to be reduced by P. amarus administration. For example, gamma-glutamyl transpeptidase activity was decreased from 20.3 +/- 6.7 mmol/min/mg protein to almost normal levels (2.8 +/- 0.9) by 750 mg/kg body weight of the extract. Similarly glutathione S-transferase activity (1317.6 +/- 211 n mol/min/mg protein) and glutathione reductase (368 +/- 66) levels in the MNNG treated group were found to be lowered to 494.8 +/- 76 and 192 +/- 45, respectively, while reduced glutathione (GSH) was increased from 4.6+/- 0.9 to 8.5+/-1.4 n mol/min/mg protein. AgNOR dots and clusters, indicators of cellular proliferation, which were increased by MNNG treatment, became near to normal in P. amarus treated animals.

Cancer preventive potential of Momordica charantia L. against benzo(a)pyrene induced fore-stomach tumourigenesis in murine model system.

Bitter melon ( Momordica charantia Linnaeus) fruit extract was tested against 3,4 benzo(a)pyrene [B(a)P] induced forestomach papillomagenesis in Swiss albino mice. Extract of M. charantia in two concentrations, 2.5 and 5% of standard mice feed was used for the short-term and long-term studies. A significant decrease in tumour burden was observed in short and long-term treatment. Also, total tumour incidence reduced to 83.33% with 2.5% dose and 90.90% with 5% dose in short term treatment, while in long-term treatment tumor incidence decreased to 76.92% with 2.5% dose and 69.23% with 5% dose of M. charantia. The possible mechanism involved in the cancer chemoprevention has also been discussed.

Ossification of the N-methyl-N'-nitro-N-nitrosoguanidine-induced small intestine adenocarcinomas in rats

Eighty rats out of 233 developed malignant tumors in the stomach and small intestine by administration of 100 micrograms/ml N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water for 28 weeks. Fifteen lesions (30%) among the 50 small intestinal carcinomas showed ossification in the tumor, while none in the sarcomas (12 lesions) or gastric adenocarcinomas (59 lesions) showed ossification. Multifocal heterotopic bone formation was found within stroma in close approximation to the neoplastic glands. The islands of bone trabeculae were covered by osteoblast-like cells, and abundant fibroblasts in loose stroma gathered around the bony islands which enclosed osteocytes in lacunae. Neither osteoclast nor cartilage was identified. In 5 cases, ossification was extensive, which comprised the major portion of the stroma. In contrast, intraluminal calcification without ossified foci were occasionally seen in the gastric carcinoma. Ossification of the intestinal tumors correlated to the degree of mucin content (p<0.05, chi square with Yates' correction), degree of neutrophilic infiltration (p<0.05), and size of the tumor (p<0.1). (The average size of the ossified tumor was 21.5 +/- 4.0 mm, while that of nonossified tumors was 12.5 +/- 1.9 mm). The degree of tumoral necrosis, desmoplasia or depth of invasion did not seem to be related to the ossification of the tumor. The ossification rate of this experimental model was much higher than in human cases. Various histologic alterations, such as mucin leakage, inflammatory cell infiltration, necrosis and/or fibrosis, which might be caused by continuous stimulation of the strong carcinogen, may play some role in the ossification of experimental tumors.