Paving the way for more precise diagnosis of EcPV2-associated equine penile lesions.

BACKGROUND: There is growing evidence that equine papillomavirus type 2 (EcPV2) infection is causally associated with the development of equine genital squamous cell carcinomas (SCCs). Early stages of disease present clinically as plaques or wart-like lesions which can gradually progress to tumoural lesions. Histologically these lesions are inconsistently described as benign hyperplasia, papilloma, penile intraepithelial neoplasia (PIN), carcinoma in situ (CIS) or SCC. Guidelines for histological classification of early SCC precursor lesions are not precisely defined, leading to potential misdiagnosis. The aim of this study was to identify histologic criteria and diagnostic markers allowing for a more accurate diagnosis of EcPV2-associated equine penile lesions. RESULTS: A total of 61 archived equine penile lesions were histologically re-assessed and classified as benign hyperplasia, papilloma, CIS or SCC. From these, 19 representative lesions and adjacent normal skin were comparatively analysed for the presence of EcPV2 DNA and transcripts using PCR and RNA in situ hybridisation (RISH). All lesional samples were positive by EcPV2 PCR and RISH, while adjacent normal skin was negative. RISH analysis yielded signal distribution patterns that allowed distinction of early (hyperplasia, papilloma) from late stage lesions (CIS, SCC). Subsequently, the 19 lesions were further assessed for expression of p53, Ki67, MCM7 and MMP1 by immunohistochemistry (IHC). All four proteins were expressed in both normal and lesional tissue. However, p53 expression was up-regulated in basal keratinocyte layers of papillomas, CIS and SCCs, as well as in upper keratinocyte layers of CIS and SCCs. MCM7 expression was only up-regulated in upper proliferating keratinocyte layers of papillomas, CIS and SCCs. CONCLUSION: This study proposes combining a refined histological protocol for analysis of equine penile lesions with PCR- and/or RISH based EcPV2-screening and p53/MCM7 IHC to more accurately determine the type of lesion. This may help to guide the choice of optimum treatment strategy, especially at early stages of disease.

Effect on nutritional markers of a model of aberrant crypt foci induced by azoxymethane and sodium dextran sulfate in Sprague Dawley rats / Efecto sobre marcadores nutricionales de un modelo de focos de criptas aberrantes inducidos por azoximetano y dextrano de sulfato sódico en ratas Sprague Dawley

Introduction: aberrant crypt foci (ACF) are colon preneoplastic lesions that can be used as a tool to study preventive processes for colorectal cancer (CRC). This model consists of initiation induced by azoxymethane (AOM) and promoted by sodium dextran sulfate (DSS), simulating human colonic carcinogenesis in a rat model. There is no direct information on the effects of this process on nutritional markers. Objective: to determine the effect on nutritional markers after the induction of ACF by AOM/DSS in a rat model. Methods: ACF were induced in 24 four-week-old Sprague Dawley male rats by administration of 2 AOM injections (10 mg/kg) and 7 days of 2% DSS in their drinking water. Body weight gain, food and fluid intake, weight of sacrificial organs, nutritional biochemical profiles, liver and kidney toxicity were evaluated. Cell counts in blood were also performed and histological sections evaluated in specific organs. The model was confirmed with identification and counts of ACF. Half of the rats were sacrificed at the sub-chronic stage and the rest at the chronic stage. Results: at the sub-chronic stage, changes in the liver and colon weight, and in the lymphocyte count were observed. For both stages, histopathological damage was observed in liver, kidney and colon, along with alterations in serum glucose levels. Conclusions: the model for proposed ACF can be used at the sub-chronic stage without the need for observation at the chronic stage. More research is needed to determine the mechanism of the observed effects

Introducción: los focos de criptas aberrantes (ACF) son lesiones preneoplásicas en colon que pueden ser utilizados como herramienta para estudiar procesos preventivos para el cáncer colorectal (CCR). Este modelo consiste en la iniciación inducida por azoximetano (AOM) y promovida por dextrano sulfato sódico (DSS) simulando una carcinogénesis colónica humana en un modelo de rata. No existe información directa de los efectos sobre marcadores nutricios para este proceso. Objetivo: determinar el efecto sobre marcadores nutricios tras la inducción de ACF por AOM/DSS en un modelo de rata. Métodos: se utilizaron veinticuatro ratas machos Sprague Dawley de 4 semanas para la inducción de ACF por administración de 2 inyecciones de AOM (10 mg/kg) y 7 días de DSS al 2% en el agua para beber. Se evaluó la ganancia de peso corporal, el consumo de alimento y de líquidos, el peso de órganos al sacrificio, perfiles bioquímicos nutricios, de toxicidad hepática y renal. Asimismo, se realizaron conteos celulares en sangre y se evaluaron cortes histológicos en órganos específicos. El modelo se confirmó con la identificación y conteos de ACF. Se sacrificó la mitad de las ratas en etapa subcrónica y las demás en etapa crónica. Resultados: en la etapa subcrónica se observaron cambios entre grupos en el peso del hígado y colon, y en el conteo de linfocitos. En ambas etapas se observaron daños histopatológicos en hígado, riñón y colon, así como alteraciones en los niveles de glucosa sérica. Conclusiones: el modelo para ACF propuesto puede ser utilizado en etapa subcrónica sin necesidad de llevarlo a tiempo crónico. Es necesaria más investigación para determinar el mecanismo de los efectos observados

Diagnostic Utility of Cytokeratin-5 for the Identification of Proliferative Inflammatory Atrophy in the Canine Prostate.

Proliferative inflammatory atrophy (PIA), which is comprised of highly proliferative but atrophic prostate epithelial cells in association with chronic inflammation, is considered a risk lesion for prostate cancer in men, while its role in canine prostate carcinogenesis is still unknown. We evaluated the value of immunohistochemical labelling for the basal cell marker cytokeratin-5 (CK5) in identifying PIA lesions in 87 samples of formalin-fixed and paraffin wax-embedded canine prostate. Canine PIA showed cytological features identical to the human counterpart and in most cases was associated with chronic lymphoplasmacytic inflammation. PIA lesions were identified in a higher number of CK5-labelled slides (43 out of 87) compared with slides stained by haematoxylin and eosin (HE) (24 out of 87). This lesion was frequently present in normal, hyperplastic and neoplastic canine prostates, although it was underestimated on evaluation of HE-stained slides. Therefore, CK5 can be considered a useful basal cell marker with high sensitivity and specificity for PIA.

Investigation of c-KIT and Ki67 expression in normal, preneoplastic and neoplastic canine prostate.

BACKGROUND: c-KIT expression has been related to bone metastasis in human prostate cancer, but whether c-KIT expression can be similarly classified in canine prostatic tissue is unknown. This study assessed c-KIT and Ki67 expression in canine prostate cancer (PC). c-KIT gene and protein expression and Ki67 expression were evaluated in forty-four canine prostatic tissues by immunohistochemistry, RT-qPCR and western blot. Additionally, we have investigated c-KIT protein expression by immunoblotting in two primary canine prostate cancer cell lines. RESULTS: Eleven normal prostates, 12 proliferative inflammatory atrophy (PIA) prostates, 18 PC, 3 metastatic lesions and two prostate cancer cell cultures (PC1 and PC2) were analysed. The prostatic tissue exhibited varying degrees of membranous, cytoplasmic or membranous/cytoplasmic c-KIT staining. Four normal prostates, 4 PIA and 5 prostatic carcinomas showed positive c-KIT expression. No c-KIT immunoexpression was observed in metastases. Canine prostate cancer and PIA samples contained a higher number of Ki67-positive cells compared to normal samples. The median relative quantification (RQ) for c-KIT expression in normal, PIA and prostate cancer and metastatic samples were 0.6 (0.1-2.5), 0.7 (0.09-2.1), 0.7 (0.09-5.1) and 0.1 (0.07-0.6), respectively. A positive correlation between the number of Ki67-positive cells and c-KIT transcript levels was observed in prostate cancer samples. In the cell line, PC1 was negative for c-KIT protein expression, while PC2 was weakly positive. CONCLUSION: The present study identified a strong correlation between c-KIT expression and proliferative index, suggesting that c-KIT may influence cell proliferation. Therefore, c-KIT heterogeneous protein expression among the samples (five positive and thirteen negative prostate cancer samples) indicates a personalized approach for canine prostate cancer.

Flaxseed and its components differentially affect estrogen targets in pre-neoplastic hen ovaries.

Flaxseed has been studied for decades for its health benefits that include anti-cancer, cardio-protective, anti-diabetic, anti-inflammatory properties. The biologically active components that mediate these effects are the omega-3 fatty acids and the lignan, secoisolariciresinol diglucoside. We have previously shown that whole flaxseed supplemented diet decreases the severity and incidence of ovarian cancer while a 15% dose of flaxseed is most protective against inflammation and estrogen-induced chemical and genotoxicity. The objective of this study was to dissect the independent effects of the two flaxseed components on estrogen signaling and metabolism. Two and half year old hens were fed either a control diet, 15% whole flaxseed diet, defatted flax meal diet or 5% flax oil diet for 3 months after which the animals were sacrificed and blood and tissues were harvested. Whole flaxseed diet caused a decrease in expression of ERα. ERα target gene expression was assessed using RT(2) profiler PCR array. Some targets involved in the IGF/insulin signaling pathway (IRS1, IGFBP4, IGFBP5) were downregulated by flaxseed and its components. Flaxseed diet also downregulated AKT expression. A number of targets related to NF-kB signaling were altered by flaxseed diet including a series of targets implicated in cancer. Whole flaxseed diet also affected E2 metabolism by increasing CYP1A1 expression with a corresponding increase in the onco-protective E2 metabolite, 2-methoxyestradiol. The weak anti-estrogens, enterolactone, enterodiol and 2-methoxyestradiol, might be working synergistically to generate a protective effect on the ovaries from hens on whole flaxseed diet by altering the estrogen signaling and metabolism.

Precáncer y cáncer bucal / Oral precancer and cancer

Se revisa el concepto de lesiones precancerosas orales, de cáncer oral y su diagnóstico precoz. Con las palabras clave: premalignant oral lesions prevention se realiza una búsqueda de los 10 últimos años. También se buscan los ensayos clínicos desde enero de 2011 hasta la actualidad con las palabras clave: oral cancer prevention AND dentistry. Se destaca que no hay cambios significativos relacionados con el concepto de lesión precancerosa y cáncer, y que en cuanto al diagnóstico precoz, si bien se describen numerosos métodos de cribado, la biopsia sigue siendo la prueba más útil y, por tanto, imprescindible, más aún si consideramos las nuevas posibilidades de estudios moleculares (AU)

We reviewed the concept of oral precancerous lesions, oral cancer, and the possibility of early diagnosis. With the keywords: premalignant oral lesions prevention, a search was performed over the past 10 years. Also clinical trials are searched from January 2011 until today with the keywords: oral cancer prevention AND dentistry. It is emphasized that there can be no significant changes related to the concept of precancerous lesions and cancer, and those relating to the early diagnosis. Despite the numerous described methods of screening, biopsy remains the most useful test, and therefore it is essential, mainly if we consider the new possibilities of molecular studies (AU)

Spontaneous amphophilic focus in the liver of a young Sprague-Dawley rat.

Altered hepatocellular focus was histopathologically observed in the liver of a 6-week-old Sprague-Dawley rat. The hepatocytes within this lesion had diffusely eosinophilic cytoplasm with scattered basophilia and slightly enlarged nuclei with prominent nucleoli. Based on these cytological characteristics, the lesion of these hepatocytes was classified as an amphophilic focus. This is the first report to describe spontaneous amphophilic focus in a young rat.

Histological and immunohistochemical identification of atypical ductal mammary hyperplasia as a preneoplastic marker in dogs.

This study describes and evaluates the morphological and molecular relationship between canine mammary ductal hyperplasias with atypia and canine mammary neoplasias. Ductal hyperplasia was identified in association with malignant neoplasia in 56 of the 115 cases (48,8%), and although ductal hyperplasia without atypia was the type most frequently noted in the cases, most examples of hyperplasia with atypia were associated with mammary tumors. Estrogen receptor, E-cadherin, and cytokeratins 1, 5, 10 and 14 (CK34bE12) expression was quite lower than in normal mammary tissue, and HER2 overexpression was absent in all proliferative cells of ductal hyperplasia. The Ki-67 expression, epidermal growth factor receptor and progesterone receptor expression appeared higher in those hyperplastic lesions analyzed than in normal mammary glands. These findings suggest that canine mammary atypical hyperplasia may play an important role in the process of malignant neoplastic transformation, with molecular alterations that are similar to precursor lesions reported in humans.

Intralobar nephroblastematosis in a nine-week-old Wistar rat.

Intralobar nephroblastematosis (ILNB) is a precursor lesion to the development of nephroblastoma (NB) in rats. Unilateral ILNB was observed in the kidney of a nine-week-old female Wistar rat (Crl:WI) from a short-term toxicity study. Clinical pathology and urinalysis did not reveal altered renal function. This microscopic, unencapsulated lesion consisted of basophilic sheets of blastemal cells that did not include a prominent mesenchymal component. These cells expanded in the interstitium, which trapped and compressed few normal renal tubules. The blastemal cells moderately differentiated to form rosettes, primitive tubules, and a glomeruloid body. Multifocally, the lumen of primitive tubules contained eosinophilic secretions with basophilic material in the center. The diagnostic criteria used were compared and differentiated with renal dysplasia, nephrogenic rest, NB in rats, and with that of the identical lesion in children.

Antioxidative and modifying effects of a tropical plant Azadirachta indica (Neem) on azoxymethane-induced preneoplastic lesions in the rat colon.

The purpose of the present study was to examine whether Neem leaf (Azadirachta indica) has short-term chemopreventive effects on endpoint preneoplastic lesions involved in rat colon carcinogenesis and might also exert antioxidative activity. Forty- two male F344 rats were randomly divided into 6 experimental groups. Groups 1 to 4 were given a subcutaneous injection of azoxymethane (AOM, 20 mg/kg body weight) once a week for 2 weeks. Starting one week before the first injection of AOM, rats in groups 2 to 4 received an aqueous extract of Neem leaf (20, 100, and 250 mg/kg, respectively) by gavage 3 times per week, for 5 weeks. Rats in group 5 also were given the Neem extract by gavage feeding 3 times per week for 5 weeks, while group 6 served as untreated controls. The experiment was terminated 5 weeks after the start. Dietary feeding of the Neem extract at all dose levels significantly inhibited the induction of aberrant crypt foci (ACF) (P<0.0002), when compared to the AOM-treated group (group 1). In groups 2 to 4, treatment of rats with the Neem extract also significantly decreased the proliferating cell nuclear antigen (PCNA) labeling indices (P<0.0006) of colon epithelium and ACF. Moreover, the Neem extract also showed antioxidative activity. The finding that dietary Neem has possible chemopreventive effects in the present short-term colon carcinogenesis bioassay suggests that longer-term exposure may cause suppression of tumor development.

Incipient spontaneous granulosa cell tumour in the gerbil, Meriones unguiculatus.

In 167 cases of granulosa cell tumour (GCT) in the gerbil, Meriones unguiculatus, 42.5% (71 cases) were in the ovaries, with no evidence of macroscopic lesion. In this paper, we describe the common findings in the incipient--microscopic--type of this spontaneous ovarian tumour occurring in gerbils younger than two years of age.

Equivocal impact of transplacental and lactational exposure to a food-derived carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, on prostate and colon lesion development in F344 rats.

The carcinogenic potential of maternal dietary exposure to 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated with the focus on the prostate and mammary glands and colons of the offspring. PhIP-DNA adducts were immunohistochemically detected in all three organs of 3-week-old animals after dams had received 200 ppm PhIP in the diet from 4 weeks before mating to weaning. The sites were essentially the same as in adult rats, suggesting that the distribution of bioactivating enzymes for PhIP do not differ greatly. Ki-67 labeling indices were increased only in the colons of the female offspring at 3-weeks of age. Development of preneoplastic and neoplastic lesions in the prostate and colon was not enhanced when the rats were maintained on PhIP-free diet until 63 weeks of age, except for significant increase in multiplicity of aberrant crypt foci in the females. The present findings indicate that PhIP exposure via placenta and breast milk may be important but that high doses and long periods may be necessary for tumor development.

Preventive effects of extract of leaves of ginkgo (Ginkgo biloba) and its component bilobalide on azoxymethane-induced colonic aberrant crypt foci in rats.

The modifying effects of dietary feeding of extract of leaves of ginkgo (Ginkgo biloba) (EGb) and bilobalide isolated from EGb on the development of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) were investigated in male F344 rats. We also assessed the effects of EGb and bilobalide on proliferating cell nuclear antigen (PCNA) index in 'normal-appearing' crypts and activities of detoxifying enzymes of cytochrome P450 (CYP), glutathione S-transferase (GST) and quinine reductase (QR) activity in the liver. To induce ACF, rats were given two weekly subcutaneous injections of AOM (20 mg/kg body wt). They also received the experimental diets containing EGb (50 or 500 ppm) and bilobalide (15 or 150 ppm) for 4 weeks, starting 1 week before the first dosing of AOM. AOM exposure produced a substantial number of ACF (106 +/- 10) at the end of the study (week 4). Dietary administration of EGb and bilobalide caused significant reduction in the frequency of ACF: 50 ppm EGb, 73 +/- 17 (31% reduction, P < 0.001); 500 ppm EGb, 56 +/- 13 (47% reduction, P < 0.001); 15 ppm bilobalide, 79 +/- 17 (25% reduction, P < 0.001); and 150 ppm bilobalide, 71 +/- 30 (33% reduction, P < 0.01). Immunohistochemically, EGb or bilobalide administration significantly lowered PCNA index in normal-appearing crypts. Feeding with EGb or bilobalide increased activities of CYP as well as GST and QR in the liver. These findings might suggest possible chemopreventive ability of EGb or bilobalide, through alterations in cryptal cell proliferation activity and drug metabolizing enzymes' activities, in colon tumorigenesis.

Cyclin D1 expression in pre-cancerous and cancerous lesions of the canine mammary gland.

Overexpression of cyclin D1, the regulatory subunit of cyclin-dependent kinases (cdk4 and cdk6) involved in cell cycle control, has often been found in breast cancer and other types of human cancer. Increased expression, or stability, of cyclin D1 molecules may cause sufficient cdk4 activation to produce retinoblastoma protein phosphorylation independently of mitogenic signals; this results in commitment of cells to the G1 phase at mitosis. In the present study, cyclin D1 expression was investigated in pre-cancerous and cancerous lesions of the canine mammary gland by a complex experimental approach, which included Western blot and immunohistochemical analysis of cyclin D1 and the related molecular system. Furthermore, to define relationships between cell growth and expression of cyclin D1, proliferative activity was studied by the AgNOR technique. The study provided the following information. Cyclin D1 overexpression was largely independent of the type of proliferative anomaly. Indeed, cyclin D1 was expressed in 60% of the pre-cancerous lesions and in 44% of cancerous lesions. Mitotic activity and cyclin D1 expression were related: mammary lesions that expressed cyclin D1 showed a high proliferative ratio, the opposite being true of cyclin D1-negative cell populations. This study may contribute to the establishment of an animal model for anti-cancer research based on cyclin D1 suppression or cdk inactivation, or both.

Tenascin expression in normal, hyperplastic, dysplastic and neoplastic canine mammary tissues.

Mammary tumours are the most common neoplasias of female dogs and may have a complex histological pattern with both epithelial and spindle cells participating in the transformation process. A frequent feature of these tumours is chondroid or bone metaplasia of the extracellular matrix, which mainly occurs in areas of proliferated spindle-shaped cells, probably of myoepithelial origin. The present study evaluates immunohistochemically the expression of tenascin in 186 surgical samples of canine mammary tissues, ranging from normality to neoplasia. Tenascin was present in all mammary tissues studied, with an increased expression in remodelling situations and in neoplastic lesions. Basement membrane was the most frequently labelled structure, but stromal tissue was more often and widely labelled in neoplastic lesions. The extracellular matrix was positive in solid and anaplastic carcinomas as well as in spindle cell proliferation areas. Tenascin expression in extracellular matrix was also abundant in areas of initial chondroid metaplasia and, with variable extension, in almost all cartilage islands of mixed tumours. In well differentiated secretory areas only apical granules of luminal cells were positive, suggesting a different pattern of tenascin expression during secretory differentiation. The digestion of chondroitin sulphate significantly improved the labelling for tenascin when a co-expression of these two molecules was present. Although our results suggest that tenascin cannot be used as a marker of transformation or of malignancy in canine mammary oncology, it is clear that this molecule plays an important role in proliferation and differentiation processes in the canine mammary gland.

Hypercalcaemia associated with chronic lymphocytic leukaemia in a Giant Schnauzer.

A 7-year-old male Giant Schnauzer was referred with a history of severe vomiting, lethargy, weight loss, polydipsia and polyuria. Detailed investigations revealed leucocytosis with a marked lymphocytosis, mild non-regenerative anaemia, thrombocytopenia, hypercalcaemia and azotaemia. Circulating lymphocytes were small and well-differentiated, and the same lymphoid population was present in bone marrow. Chronic lymphocyctic leukaemia with associated paraneoplastic hypercalcaemia was diagnosed. Immunohistochemical staining of a bone marrow biopsy revealed a neoplastic B-cell line expressing CD79. The dog responded to therapy with prednisolone and chlorambucil for a period of 8 months.

Tamoxifen suppresses histologic progression to atypia and DCIS in MCFIOAT xenografts, a model of early human breast cancer.

We evaluated the effects of tamoxifen on the growth and progression of MCFIOAT xenografts, an estrogen responsive model of human breast tumor progression, in which cells are injected orthotopically into the mammary fat pad of female nude mice. At 10 weeks following implantation, histologic sections of each graft were evaluated microscopically for histologic lesions analogous to human breast tumor progression, graded as simple hyperplasia, complex hyperplasia, atypical hyperplasia, ductal carcinoma in situ and invasive carcinoma. Three out of five xenografts in (endocrine intact) control animals progressed to atypical hyperplasia, one progressed to ductal carcinoma in situ and one to invasive carcinoma. The latter two control grafts also contained foci of putative precursor lesions (i.e. atypical hyperplasia and in situ carcinoma, respectively). Tamoxifen supplemented xenografts (N= 17) were uniformly smaller than controls, but contained invasive carcinoma in a similar proportion (4/17, 24%). However, none of these grafts exhibited ductal carcinoma in situ and only one contained atypical hyperplasia. Most grafts in tamoxifen supplemented animals (10/17, including all four with carcinomas) showed complex hyperplasia, which typically dominated the graft. We conclude that tamoxifen selectively inhibits the appearance or growth of preinvasive index lesions. Development of malignancy in the absence of such precursors, though, implies selection for alternative histogenetic pathways as a result of endocrine manipulation.

Increased pathology incidence in the forestomach of rats maintained on a diet containing ivermectin and given a single dose of N-methyl-N1-nitro-N-nitrosoguanidine.

Ivermectin is widely used against parasitic infections in veterinary and human medicine and was found to promote the growth of lesions leading to neoplasia when given continuously in the diet to Wistar rats receiving a single low dose of N-methyl-N1-nitro-N-nitrosoguanidine (MNNG). No tumors or pathological lesions were observed in the forestomach of the control animals or those given ivermectin alone. However, compared to animals receiving MNNG alone, rats maintained on a diet containing ivermectin (2 ppm) and given MNNG (12.5 mg/kg) by gavage showed an increased number of neoplasms (9/26 vs 3/18; p = 0.30) and a statistically significant fourfold increase in the number of pathological lesions (18/26 vs 3/18; p = 0.002), which include preneoplasia in the forestomach. In all cases, the pathological lesions were more severe in the animals receiving ivermectin and MNNG, compared to those receiving MNNG alone.

Failure to induce tumors in the large intestine of Capuchin mokeys (Cebus apella) by using 1,2-dimethylhydrazine.

The purpose of this study was to produce tumors in the large intestine of Capuchin Monkeys (Cebus apella) by the administration of the colonotropic carcinogen 1,2-dimethylhydrazine (DMH). The subjects were 12 monkeys, all males, age 30 months, with a mean weight of 2.858 kg. The DMH was administered subcutaneously to six of the monkeys at a dosage of 25 mg/kg of body weight once a week for 16 weeks; control monkeys received an equivalent volume of the stock solution without DMH. Twenty months after administration of the first dose, the animals were sacrificed. None of the monkeys showed intestinal tumors. Samples of the gastrointestinal tract were removed, fixed, and stained according to standard histological techniques. Histological changes were seen in all of the DMH-treated animals; these consisted of glandular hyperplasia and hyperplasia of the epithelium overlying the lymphoid nodules. In addition, foci of dysplasia were found in three of the animals. Our results suggest that the DMH induced pre-neoplastic changes, characterized by hyperplasia and dysplasia, in the mucosa of the large intestine.

Immunohistochemical study of the inflammatory infiltrate associated with equine squamous cell carcinoma.

The distribution of T (CD3), B (CD79) lymphocytes, immunoglobulin (IgG, IgM and IgA)-producing plasma cells, macrophages (lysozyme, Mac387) and MHC Class II antigen was analysed in the inflammatory infiltrate associated with 19 equine squamous cell carcinomas (SCCs) and six cases of precancerous lesions (actinic keratosis). The SCCs came from the penis (11 cases), conjunctiva (four), skin (two), nasal cavity (one) and oral cavity (one). Seven cases were well-differentiated and 12 moderately differentiated. Nine cases showed no invasion of peritumoral deep tissues (locally invasive), whereas the remaining 10 cases were highly invasive. An abundant inflammatory infiltrate was associated with the majority of the SCCs and with lesions of actinic keratosis. This infiltrate was composed mainly of CD3(+)T lymphocytes, CD79(+)B cells and numerous IgG(+)plasma cells; IgM- and IgA-producing plasma cells were scarce and variable, respectively. Macrophages were usually numerous. Macrophages, lymphocytes, intra-epithelial dendritic cells and fibroblasts expressed MHC Class II antigen. No significant correlation was found between the nature of the inflammatory infiltrate and the SCC histological grade or degree of invasion, suggesting that the local anti-tumour immune response failed to prevent tumour invasion or metastasis. MHC Class II was expressed by a variable number of neoplastic epithelial cells in four SCCs, all of which were only locally invasive. In addition, in areas where SCC cells expressed Class II antigen, numerous CD3(+)T lymphocytes were present and some of them were associated with degenerate tumour cells. These findings suggest that the expression of MHC Class II by neoplastic cells induces an improved local anti-tumour immune response.