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The result of the reaction of free radicals with biomolecules is the formation of substances with the potential of inducing oxidative damage, a condition known as oxidative stress. There are voluminous literature data reporting the association, both as a cause and as a consequence, between different diseases and oxidative stress. In this study, 144 female dogs with mammary neoplasia were analyzed. The animals were submitted to clinical evaluation for disease staging, hematological evaluation, serum biochemistry (renal and hepatic function tests), and dosage of the oxidative damage biomarker, malondialdehyde (MDA), at the time of its approach and 30 days after treatment. A control group of 100 healthy animals was also submitted to determination of serum MDA levels. The mean age of the animals affected by mammary neoplasms was 9.88±2.95 (4 to 14) years, while in healthy animals it was 2.31±1.90 years (1 to 6). Of the 144 animals, 113 (78.9%) had malignant neoplasms, and 15, 21, 46, 17 and 14 animals were in clinical stage I, II, III, IV and V respectively and the carcinoma in a mixed tumor was the most frequent histological pattern in this group (26%). Thirty-one animals were diagnosed with benign neoplasms and mammary adenoma was the most frequent histological pattern in 15 animals (51.61%). Hematological changes in the preoperative period were observed in 44 (38.9%) and 12 (38.7%) animals with malignant and benign neoplasias, respectively, and there was a positive correlation between anemia and higher levels of MDA (P=0.0008) for animals with malignant tumors. Regarding serum biochemical parameters, the most frequent alterations in animals with malignant neoplasms were elevated ALT levels in 12 animals (10.6%), creatinine in 10 animals (8.84%) and urea in eight animals (7.07%). Females with benign neoplasms presented less occurrence of changes in these parameters. In the group of healthy animals (control), the mean serum MDA values were 12.08±4.18, whereas in the pre-treatment group, mean MDA was 24.80±5.74 for bitches with benign neoplasms and 32.27±10.24 for bitches with malignant tumors. A significant increase (P

As neoplasias mamárias em cadelas são afecções de significativa importância em medicina veterinária pela sua alta frequência, além de serem modelo para o estudo do câncer de mama na mulher. Nesse sentido, se faz necessária a realização de estudos continuados acerca da frequência de tumores e suas características clinicopatológicas. Constituem ainda um grupo heterogêneo de tumores quanto aos padrões histológicos e comportamento biológico, o que torna mais complexo e urgente a identificação de fatores de prognóstico e que possibilitem diagnosticar e tratar de forma mais eficaz animais portadores de tumor de mama. Nos últimos anos, tem se intensificado estudos dirigidos à identificação de marcadores moleculares envolvidos nos inúmeros eventos celulares que ocorrem durante a carcinogênese, como crescimento e diferenciação celular, proliferação, invasão e metástase. O receptor do fator de crescimento epidérmico humano tipo 2 (HER-2) é uma glicoproteína de membrana da família tirosina-quinase, codificada por um gene de mesmo nome, diretamente relacionada a mudanças significativas na proliferação celular e sobrevivência das células tumorais. Durante o processo de mutação desse gene ocorre hiperativação da cascata de sinalização intracelular, que resulta em rápido crescimento das células tumorais. Na mulher, a superexpressão de HER-2 está associada a neoplasias mamárias cujos parâmetros morfológicos sugerem malignidade e pior prognóstico, resultando em alta taxa de recidiva e de mortalidade no estágio inicial da doença, além de elevada incidência de metástases. Entretanto, na cadela, estudos que investigaram o papel do HER-2 nas neoplasias mamárias, com emprego da imunohistoquímica, não são consensuais até então, mantendo obscuro o significado da sobrexpressão de HER-2 nestas neoplasias. Com intuito de auxiliar na determinação de fatores prognósticos fidedignos para os tumores mamários nas cadelas, o presente trabalho teve como objetivos: determinar a prevalência de lesões mamárias diagnosticadas em cadelas no Laboratório de Patologia Veterinária da Universidade Federal de Uberlândia entre 2004 e 2014, bem como a relação entre aspectos epidemiológicos (idade e raça) e clínicopatológicos (ulceração, tamanho do tumor e comportamento biológico) na ocorrência dos tumores de mama; e verificar a expressão de HER-2 em carcinomas mamários de cadelas e sua relação com o tipo e grau histológico, idade das cadelas, metástase em linfonodos e à distância, tamanho tumoral e estadiamento clínico. Mammary tumors in female dogs are important diseases in veterinary medicine due to their high frequency, besides being a model for the study of breast cancer in women. So, it is necessary to continuous studies on the frequency of tumors and their clinicopathological characteristics. They also constitute a heterogeneous group of tumors in correlation with histological patterns and biological behavior, which makes it more complex and urgent to identify prognostic factors and to make it possible to diagnose and treat animals with mammary tumors more effectively. In the last years, there have been intensified the number of studies about the identification of molecular markers involved in the innumerable cellular events that occur during carcinogenesis, such as cell growth and differentiation, proliferation, invasion and metastasis. HER-2 is a membrane glycoprotein of the tyrosine kinase family, encoded by a gene with the same name, directly related to significant changes in cell proliferation and survival of tumor cells. During mutation process of this gene, hyperactivation of intracellular signaling cascade results in a rapid growth of tumor cells. In women, HER-2 overexpression is associated with breast neoplasms whose morphological parameters suggest poor prognosis and malignancy, resulting in a high rate of recurrence and mortality in the early stage of the disease, as well as a high incidence of metastases. However, in the female dog, until now the extensive variability of results obtained from immunohistochemical protocols proposed for molecular classification, keeps the meaning of HER-2 overexpression in these neoplasms obscure. In order to assist determination of the reliable prognostic factors for canine breast neoplasms, the present study: determined the prevalence of breast lesions diagnosed in female dogs in Laboratory of Veterinary Pathology of the Federal University of Uberlândia between 2004 and 2014, as well as the correlation between epidemiological aspects (age and breed) and clinicopathological (ulceration, tumor size and biological behavior) in the occurrence of breast tumors; verified the HER-2 expression in female mammary carcinomas of dogs and their relationship with the type and histological grade, age of patient, metastasis in lymph nodes or distants, tumor size and clinical staging. Tese (Doutorado)

Aim The main objective of the study was to describe the use of skin fold advancement flaps (SFAFs) and other reconstructive techniques for closure of large skin defects following mammary tumor excision in dogs. Materials and methods Twelve dogs underwent reconstruction of large ventral skin defects following mammary tumor excision with wide margins. Skin fold flaps (flank fold flap and elbow fold flap) were elevated from the flank and elbow region, respectively, and transposed and sutured onto the large ventral skin defect following mastectomy in all the dogs. In addition to the skin fold flaps, other reconstructive techniques such as undermining, walking sutures, and tension-relieving suture techniques were followed during surgery in the closure of large skin defects without skin tension and compromising limb mobility. The skin flap viability was assessed subjectively by gross observation of the flap such as color, temperature, capillary perfusion, and cosmetic appearance, and scoring (1-4) was done. Tissue samples were collected from a surgical site on days 3, 6, and 12 post-operatively for histopathological evaluation and healing status of the skin flap. Results All the surgical wounds healed primarily, without any major complications and the skin flap remained healthy throughout the healing process post-operatively. Distal flap necrosis was noticed in one case and necrosis of skin flap between two suture lines was noticed in another case in which the necrotized distal portion healed by secondary intention after 7 days. The mean survival of subdermal plexus flap in the above cases was 98% which was a subjective evaluation based on surface area of the skin defect measured by Image' J software and the flap dimensions. The average healing of skin flap in days was 14.91±0.86. Conclusion The SFAFs along with other reconstructive techniques help in the reconstruction of large ventral skin defects following mastectomy in dogs without much compromising limb mobility.

Los tumores mamarios caninos (TMC) representan casi la mitad de las neoplasias en la perra. La etiopatogenia de los TMC es multifactorial. En perras el efecto protector de la ovarioectomía temprana y la presencia de receptores para hormonas esteroideas en los tejidos tumorales indican que el factor hormonal esta involucrado en el desarrollo de los tumores mamarios. La presentación clínica de los TMC es muy variable, pudiendo ser únicos o múltiples. En los casos múltiples pueden ser del mismo o diferente tipo histológico. En esta revisión se presenta la clasificación histopatológica de los tumores, junto a una breve descripción de las características particulares de cada una. Si bien la cirugía es el método de elección para las neoplasias mamarias caninas, actualmente se cuenta con diferentes modalidades de terapias adyuvantes que podrían mejorar el pronóstico de la enfermedad. El objetivo del presente trabajo fue realizar una revisión y actualización de los tumores de mama en la perra, poniendo especial énfasis en la etiopatogenia, tratamiento y nuevas perspectivas creadas a partir de los avances adquiridos en oncología molecular., Canine mammary tumors (CMT) represent nearly half of bitch's neoplasias. The etiopathogeny of CMT is multifactorial. Both the protective effect of early ovarioectomy and steroid hormone receptors present in the tumor tissues show that the hormonal factor is involved in the development of mammary tumors. Clinical presentation of CMT may be unique or multiple, being the latter of the same or different histological type. The histopathological classification of tumors together with a brief description of their particular features is presented in this review. Although surgery is the best treatment for CMT, there are different adyuvant therapies that could improve the prognosis of the disease. The goal of the present work was to make an updated review of CMT, with special emphasis on its etiopathogy, treatment and new options resulting from the advances in molecular oncology., Facultad de Ciencias Veterinarias

Breast tumors are very common in small animals. There is no known cause directly related to this disease but there are some risk factors associated with the breast tumors in animals. Although no clear and consensual they are referred endocrine, genetic, diet and lifestyle factors. Focusing on the endocrine risk factor, a small study was carried out to collect data from owners of female dogs and cats who have suffered from this condition. The main objective of this work was to find out if there is any association between birth control pill administration and the occurrence of malignant / benign breast tumors in identified clinical cases. Surveys were performed in which animal data were collected, the age of the animal, when the disease was diagnosed, if the animal was taking the contraceptive pill, if the diagnosed tumor was of benign or malignant origin, if the owner was informed of the contraindications of this medicine. Older animals have a greater predisposition to mammary tumors in dog and cats (older than 7 years). And generally the owners who administer pills for reproductive control in these animals have no concept of contraindications. It is therefore important that veterinary teams (veterinarian and veterinary nurse) reinforce information actions for animal owners. info:eu-repo/semantics/publishedVersion

The mechanisms that drive ductal carcinoma in situ (DCIS) progression to invasive cancer are not clear. Studying DCIS progression in humans is challenging and not ethical, thus necessitating the characterization of an animal model that faithfully resembles human disease. We have characterized a canine model of spontaneous mammary DCIS and invasive cancer that shares histologic, molecular, and diagnostic imaging characteristics with DCIS and invasive cancer in women. The purpose of the study was to identify markers and altered signaling pathways that lead to invasive cancer and shed light on early molecular events in breast cancer progression and development. Transcriptomic studies along the continuum of cancer progression in the mammary gland from healthy, through atypical ductal hyperplasia (ADH), DCIS, and invasive carcinoma were performed using the canine model. Gene expression profiles of preinvasive DCIS lesions closely resemble those of invasive carcinoma. However, certain genes, such as SFRP2, FZD2, STK31, and LALBA, were over-expressed in DCIS compared to invasive cancer. The over-representation of myoepithelial markers, epithelial-mesenchymal transition (EMT), canonical Wnt signaling components, and other pathways induced by Wnt family members distinguishes DCIS from invasive. The information gained may help in stratifying DCIS as well as identify actionable targets for primary and tertiary prevention or targeted therapy.

Fine-needle aspiration cytology is an easy, rapid, low cost, and minimally invasive technique, consequently contributes to a faster diagnosis leading to a faster decision, mainly to provide welfare and quality of life to patients. The objective of this study was to use FNAC in specific diseases of domestic animals. One study evaluated the association between cytopathology and histopathology diagnosis of mammary tumors in female dogs and described important cytology elements to further differentiate and classify tumors; and another study described cytological findings on bovine seneciosis. The first study included 101 samples of 61 dogs from 2012 to 2014. Cytologic examination classified 96 samples as malignant tumors and five as benign. Among all malignant tumors, the most frequent was simple carcinoma (54.17%), complex carcinoma (20.83%) and malignant mixed tumor (17.71%). Carcinosarcoma (4.17%), osteosarcoma (2,08%) and squamous cell carcinoma (1,04%) were the least common. Benign tumors were complex adenomas (n=2; 40%) and mixed tumors (n=3; 60%). Cytology diagnoses were compared to histopathology with 99% accuracy, 100% sensibility and 83% specificity. Cyto-histologic correlation was 92.50% for simple carcinomas, 57.89% for complex carcinomas, 57.14% for malignant mixed tumor, 27.27% for carcinosarcomas and 100% for osteosarcomas. Myoepithelial cells in nests were seen in both complex and mixed tumors and therefore should not be considered as a cytologic feature for differential diagnosis. Mesenchymal cells (probably fibroblasts) were differentiated from myoepithelial cells by FNAC, allowing us to differentiate simple carcinomas with desmoplastic reactions from complex and mixed tumors. Magenta matrix, interpreted as condroid/osteoid, was found in malignant mixed tumors (66.66%), carcinosarcomas (63.64%), benign mixed tumors (50%), osteosarcomas (50%), and complex carcinomas (10.53%). Abundant extracellular pink and finely granular matrix throughout the background was found in six malignant mixed tumors (28.57%), three carcinosarcomas (27.27%) and two benign mixed tumors (50%). This matrix was absent in complex tumors. For this reason, it can be used as an indicator of mixed tumors. The second study was performed on a bovine liver presenting clinical signs and history of Senecio spp. poisoning. Cytology slides showed megalocytosis, the main finding on histopathology to confirm the diagnosis. FNAC is not described as a diagnostic method for Seneciosis. Cyto-histo correlation was good, suggesting that FNAC can be used as a diagnostic method for bovine Seneciosis. Consequently, our results suggest FNAC as a valid method for diagnosing malignant mammary tumors in female dogs and also have efficacy on bovine seneciosis diagnosis. These results give an early and rapid diagnosis, allowing the veterinarian to choose the best treatment option, or determine the prognosis for an animal. A citologia aspirativa por agulha fina é uma técnica fácil, rápida, de baixo custo e minimamente invasiva, que pode fornecer informações diagnósticas importantes rapidamente, principalmente para prover bem estar e qualidade de vida ao paciente. O objetivo desta tese envolveu a utilização e aplicação da citologia aspirativa por agulha fina em doenças específicas em animais domésticos. Para isso, inclui um artigo que compara o diagnóstico citopatológico de tumores mamário em cadelas, com o histopatológico e descreve elementos citológicos importantes para a diferenciação e classificação adicional dos tipos de tumores; e outro artigo que descreve os achados citológicos na seneciose em bovinos. O primeiro trabalho incluiu 101 amostras citológicas de tumores de mama de 61 cadelas entre 2012 e 2014. Destes, a análise citológica classificou 96% dos tumores malignos e 4% benignos. Entre todos os tumores mamários malignos, o mais comum foi carcinoma simples (54,17%), seguido de carcinoma complexo (20,83%) e carcinoma em tumor misto (17,71%). Carcinossarcoma (4,17%), osteossarcoma (2,08%) e carcinoma de células escamosas (1,04%) foram infrequentes. Os tumores benignos incluíram dois adenomas complexos (40%) e três tumores mistos benignos (60%). Os diagnósticos citológicos foram comparados com os histopatológicos, resultando em acurácia de 99%, sensibilidade de 100% e especificidade de 83%. A concordância diagnóstica foi de 92,5% para carcinoma simples, 57,89% para carcinoma complexo, 57,14% para carcinoma em tumor misto, 27,27% para carcinossarcoma e 100% para osteossarcoma. Células mioepiteliais foram identificadas em sete carcinomas complexos e dez carcinomas em tumor misto, por isso sua ocorrência não pode auxiliar na distinção destes dois tumores através da citologia. Células mesenquimais alongadas (prováveis fibroblastos) foram diferenciadas, através da citologia, de células mioepiteliais, o que permitiu distinguir carcinoma simples com reação desmoplásica de carcinomas complexo e mistos. Matriz magenta, interpretada como condroide e/ou osteoide, foi identificada em 66,66% dos carcinomas em tumor misto, 63,64% dos carcinossarcomas, 50% dos tumores misto benignos, 50% dos osteossarcomas e 10,53% dos carcinomas complexos. Uma matriz rosa, finamente granular e abundante ao fundo da lâmina (matriz mixoide) foi encontrada em 28,57% dos carcinomas em tumor misto, 27,27% dos carcinossarcomas e 50% dos tumores misto benignos. Este tipo de matriz foi ausente nos tumores complexos, por isso sua presença pode ser indicativa de tumores mistos. No segundo estudo foi realizada a citologia aspirativa por agulha fina do fígado de um bovino suspeito de intoxicação por Senecio spp., o que demonstrou a presença de megalocitose, principal achado histopatológico para a confirmação do diagnóstico. A CAAF na seneciose ainda não foi descrita, e os achados citológicos tiveram boa correlação com os histopatológicos, o que indica a possibilidade de incluir este método no diagnóstico precoce de seneciose em bovinos. Portanto, nossos resultados melhoram a confiabilidade da citologia aspirativa por agulha fina como método diagnóstico em tumores mamários de cadelas e demonstram a eficácia da CAAF no diagnóstico de seneciose em bovinos, possibilitando o diagnóstico precoce destas enfermidades e consequentemente fornecer ao clínico informações importantes para decisões sobre conduta e tratamento a ser selecionado.

Background: Mammary tumors are a type of neoplasia that are most commonly found in female dogs and are mostly malignant. The aim of this study, performed in the Laboratory of Veterinary Pathology of the Federal University of Uberlândia (LVP-FUU) from 2004 to 2014, was to determine the prevalence of mammary tumors in bitches and to verify the relationship between the epidemiological factors (age and breed) and clinicopathological aspects (ulceration, tumor size, and malignancy) in the occurrence of tumors.Materials, Methods & Results: A retrospective study was carried out using histopathological information retrieved from the LPV-UFU database. We collected the information on age and breed of female dogs, as well as about the location, macroscopic aspects, and histological diagnosis of mammary lesions. Only female dogs were considered for this study; a total of 911 histopathological protocols (with only one diagnosis) were analyzed along with 36 protocols that presented more than one diagnosis of mammary tumor. The age of animals ranged from one to 20 years, and the mean age was 9.99 years. The most affected breeds of dogs were: Cross breed (39.56% - 288/728) and Poodle (20.19% - 147/728). The inguinal glands were most affected by the malignant tumors (P < 0.05). A prevalence of tumors bigger than 5 cm in diameter (T3) was observed in the elderly animals (P = 0.0154) and in the inguinal mammary glands (P = 0.044). Simple carcinoma was the most frequent histological type.Discussion: Research shows that more than 40% of the tumors in bitches are located in the mammary glands, emphasizing the importance of this type of neoplasia in female dogs. Mammary tumors develop more frequently in the middle-aged and elderly bitches, with the highest occurrence being in the age range of 8 and 10 years, corroborating our observation in the present study that the mean age of bitches was 9.99 years. In this survey, a higher incidence was observed in mongrel bitches compared to that in the Poodle breed. Some authors affirm that there is no racial predisposition for the occurrence of this pathology; however, a compilation of data suggests a predisposition of at least 10 breeds, with the involvement of an as yet unidentified genetic component. Of these, six breeds (Poodle, Cocker Spaniel, Pointer, Maltese, Yorkshire Terrier, and Dachshund) were found to be predisposed to mammary tumors in this study. The percentage (49.23%) of malignant tumors found in the inguinal glands is consistent with the findings reported in literature, and might be associated with a greater amount of parenchyma, abundance of hormone receptors in these glands, and vascularization provided by the caudal superficial epigastric artery and vulvar branches of external pudendal artery. Tumor size is considered to be a prognostic factor and tumors ≤ 3 cm in diameter (T1) have a better prognosis. Consequently, the prevalence of tumors ≥ 5 cm in diameter (T3) in elderly animals is probably related to malignancy of the lesions, because tumors usually progress to a worse histological grade with time. The higher occurrence of T3 in inguinal glands might be related to the abundance of parenchyma and/or hormonal receptors in them. As in the present study, data from literature refer to the superiority of malignant histological types, with prevalence varying between 68 and 91%. When prolonged, the time between the onset of tumor and clinical evaluation may be a determinant in the progression from benign to malignant tumors. Among the malignant neoplasms, simple carcinoma was observed to be prevalent, followed by mixed tumors with carcinoma, in agreement with the results of several studies. It is concluded that mammary tumors are more prevalent in older mongrel dogs and Poodle. Attention should be paid to inguinal mammary tumors, because these are mainly malignant.

Cytological diagnosis is not generally conclusive enough to identify histopathological malignancy in canine mammary tumors (CMTs). To establish cytological examination using fine needle biopsy (FNB) samples, gene expressions of hormonal receptors, human epidermal growth factor receptor 2 (HER2), and transcription regulators (Special AT-rich binding protein 1: SATB1 and Snail) were investigated in both tissue and FNB samples of CMTs. In tissue samples of malignant CMTs, especially invasive ones, low expressions of hormonal receptors and high expressions of SATB1 and Snail were detected. On discriminant analysis of tissue samples, 73.2% of CMTs were correctly classified according to histopathological examinations. In FNB samples of malignant CMTs, low expressions of hormonal receptors were detected. On discriminant analysis of FNB samples, 74.2% of CMTs were correctly classified according to histopathological examination. In conclusion, FNB gene expressions had a utility for diagnosis of CMTs malignancy in some degree. By researching more sensitive genes for malignant CMTs, the gene examination of FNB samples from CMTs will become a useful diagnostic tool that can be performed easily without anesthesia and could predict tumor malignancy and invasion prior to surgical removal.

La técnica de inmunohistoquímica descrita por Walker y col. (1998) y Mote y col. (2001) es de utilidad para la determinación de receptores de estrógenos y de progesterona en tumores mamarios de la hembra canina. Existe bastante controversia respecto al porcentaje de receptores de estrógenos y de progesterona, con valor pronóstico o predictivo en tumores malignos caninos debido, muy probablemente, a la falta de uniformidad en criterios de inclusión de los casos en los estudios realizados. El presente trabajo se realizó en una población de 51 perras. Los tumores fueron escindidos quirúrgicamente mediante mastectomía de las glándulas afectadas. Para la determinación de receptores hormonales, se analizó la muestra con mayores características histológicas de malignidad de cada animal. Se contabilizó el porcentaje de células tumorales positivas para cada uno de los receptores (receptor de estrógeno alfa, receptor de estrógeno beta y receptores de progesterona) en los distintos estadios clínicos (I, II, II, IV). Se consideró positivo todo corte ≥ 20% de células tumorales positivas para cada uno de los receptores. Se realizó una estadística descriptiva (media y error estándar) con los animales positivos para cada uno de los receptores en los distintos estadios clínicos. En línea con reportes de otros autores, más de la mitad de caninos portadores de tumores mamarios malignos expresaron receptores de estrógenos y de progesterona. Conociendo que el comportamiento biológico de una neoplasia varía con el estadio clínico del paciente, resulta interesante estudiar la expresión de los receptores en cada uno de éstos, en animales con neoplasias mamarias malignas. Adicionalmente, a este objetivo incluye la puesta a punto la de técnica de inmunohistoquímica para la determinación de receptores hormonales en la especie. Immunohistochemical technique described by Walker et al. 1998 and Mote et al. 2001 is useful for the determination of estrogen and progesterone receptors in canine mammary tumors. There is considerable controversy regarding the percentage of estrogen and progesterone receptors that having prognostic or predictive value in malignant tumors in dogs because, most likely, the lack of uniform criteria for inclusion of cases. This study was conducted in a population of 51 female dogs. The tumors were surgically treated by mastectomy of the affected glands. For the determination of hormone receptors, the sample analyzed was showed higher histological malignancy features of each animal. It was counted the percentage of tumor cells positive for each of the receptors (estrogen receptor alpha, estrogen receptor beta and progesterone receptor) in animals in various clinical stages (I, II, III, IV). It was considered positive cut-off ≥ 20% tumor cells positive for each of the recipients. It was conducted a descriptive statistics (mean and standard error) which positive animals for each of the receptors in different clinical stages. In line with reports of other authors, more than half of canine carriers of malignant mammary tumors expressed estrogen and progesterone receptors. Knowing that the biological behavior of cancer varies with the clinical stage of the animal, objective was to study the expression of receptors in each of the clinical stages in animals with malignant mammary tumors. Additionally, this includes the preparation of the immunohistochemical technique for the determination of hormone receptors in this species. 245-253 ghermo@unq.edu.ar. Bimestral

La técnica de inmunohistoquímica descrita por Walker y col. (1998) y Mote y col. (2001) es de utilidad para la determinación de receptores de estrógenos y de progesterona en tumores mamarios de la hembra canina. Existe bastante controversia respecto al porcentaje de receptores de estrógenos y de progesterona, con valor pronóstico o predictivo en tumores malignos caninos debido, muy probablemente, a la falta de uniformidad en criterios de inclusión de los casos en los estudios realizados. El presente trabajo se realizó en una población de 51 perras. Los tumores fueron escindidos quirúrgicamente mediante mastectomía de las glándulas afectadas. Para la determinación de receptores hormonales, se analizó la muestra con mayores características histológicas de malignidad de cada animal. Se contabilizó el porcentaje de células tumorales positivas para cada uno de los receptores (receptor de estrógeno alfa, receptor de estrógeno beta y receptores de progesterona) en los distintos estadios clínicos (I, II, II, IV). Se consideró positivo todo corte ³ 20% de células tumorales positivas para cada uno de los receptores. Se realizó una estadística descriptiva (media y error estándar) con los animales positivos para cada uno de los receptores en los distintos estadios clínicos. En línea con reportes de otros autores, más de la mitad de caninos portadores de tumores mamarios malignos expresaron receptores de estrógenos y de progesterona. Conociendo que el comportamiento biológico de una neoplasia varía con el estadio clínico del paciente, resulta interesante estudiar la expresión de los receptores en cada uno de éstos, en animales con neoplasias mamarias malignas. Adicionalmente, a este objetivo incluye la puesta a punto la de técnica de inmunohistoquímica para la determinación de receptores hormonales en la especie. receptors in canine mammary tumors. There is considerable controversy regarding the percentage of estrogen and progesterone receptors that having prognostic or predictive value in malignant tumors in dogs because, most likely, the lack of uniform criteria for inclusion of cases. This study was conducted in a population of 51 female dogs. The tumors were surgically treated by mastectomy of the affected glands. For the determination of hormone receptors, the sample analyzed was showed higher histological malignancy features of each animal. It was counted the percentage of tumor cells positive for each of the receptors (estrogen receptor alpha, estrogen receptor beta and progesterone receptor) in animals in various clinical stages (I, II, III, IV). It was considered positive cut-off ³ 20% tumor cells positive for each of the recipients. It was conducted a descriptive statistics (mean and standard error) which positive animals for each of the receptors in different clinical stages. In line with reports of other authors, more than half of canine carriers of malignant mammary tumors expressed estrogen and progesterone receptors. Knowing that the biological behavior of cancer varies with the clinical stage of the animal, objective was to study the expression of receptors in each of the clinical stages in animals with malignant mammary tumors. Additionally, this includes the preparation of the immunohistochemical technique for the determination of hormone receptors in this species.