Treatment of Canine Oral Melanoma with Adjuvant Chemotherapy and Immunotherapy

Background: Melanoma is the most frequent cancer in the canine oral cavity. It shows an aggressive behavior, characterized by rapid and invasive growth and high metastatic potential. Metastasis is seen in more than 80% of dogs at time of death. Adjuvant therapy should be recommended because of potential recurrence and metastasis. Oral melanoma has a poor prognosis even when adjuvant treatments are used. There are some treatment options, but the high death rate due to the disease is still a challenge. The aim of this study was to assess the overall survival of dogs diagnosed with oral melanoma and treated with adjuvant chemotherapy and immunotherapy. Materials, Methods & Results:A retrospective analysis was carried out in 20 dogs with oral melanocytic or amelanocytic melanomas. Cases were staged according to a modified World Health Organization clinical staging system for canine oral malignant melanoma. Tumor size (T1: 4 cm), regional metastasis (N0: no metastasis; N1: metastasis) and presence of distant metastasis (M0: no metastasis; M1: metastasis) are evaluated. Then, cases were divided into 4 stages: I (T1 N0 M0), II (T2 N0 M0), III (T3 N0-1 M0, Tx N1 M0) and IV (Tx Nx M1). Diagnoses were confirmed with histopathological exam and immunohistochemistry (IHC) when necessary. In poorly differentiated neoplasms, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Animals were divided into 2 groups: dogs submitted to surgery alone were included in group 1 (G1); dogs submitted to surgery associated with adjuvant chemotherapy with four 21-day cycles of carboplatin (300 mg/m2) and immunotherapy with six 7-day cycles of interferon-α (3 x 106 IU/m2) were included in group 2 (G2). Twenty dogs diagnosed with oral melanoma were evaluated: 3 were included in G1 and 17 in G2. Considering clinical staging of the dogs: 7 stage II, 12 stage III and only 1 stage IV. There was no stage I patients. In poorly differentiated neoplasias, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Patient follow-up was obtained through the evaluation of patient records and telephone interviews with owners. The overall survival time (OS) was defined by the period (in days) between the date of surgical excision and the death caused by the disease. Median overall survival time was 86 days for animals in G1 and 894 days for animals in G2 (P = 0.01). Discussion: Carboplatin was considered an appropriate cytostatic drug to treat microscopic disease in oral melanoma. INF-α was chosen for immunotherapy in this study because it promotes immune system stimulation associated with an indirect antiproliferative effect on neoplastic cells. The association of INF-α and carboplatin resulted in a significant increase in overall survival, when compared to the literature, suggesting that association of chemotherapy and immunomodulation is an important strategy in the treatment of canine oral melanoma. Controlled prospective randomized trials are necessary to confirm the benefits of chemotherapy and immunotherapy association to treat canine oral melanoma. Adjuvant therapy with chemotherapy and immunotherapy was considered effective to increase overall survival and maintained quality of life of dogs diagnosed with oral melanoma

Histomorphological and Immunophenotypic Characterization of Feline Injection Site-Associated Sarcoma

Background: Feline Injection Site-Associated Sarcoma (FISS) is a mesenchymal neoplasia of aggressive behavior that develops in sites where vaccine or drugs were administered. FISS is clinically characterized by the appearance of a solitary firm nodule or a diffuse mass, adhered to tissues, in regions associated to vaccine or drug applications. Despite low prevalence, tumor recurrence rates can reach 80%. FISS present more aggressive histological characteristics when compared to sarcomas not associated to injection sites. The aim of this paper is to contribute towards the understanding of the biological behavior of FISS.Materials, Methods & Results: Sixteen samples of FISS were analyzed. Fibrosarcomas were the most frequent histological subtype (62.5%). Malignant peripheral nerve sheath tumor was diagnosed in 18.75% cases. Ten (62.5%) FISS were classified as grade II; 4/16 (25%) grade I, and 2/16 (12.5%) grade III. Cox-2 overexpression occurred in 3/16 (18.75%) samples, with positive correlation between Cox-2 expression and cellularity (r = 0.696, P = 0.003). Mitotic index lower than 9 events was found in 11/16 (68.7%) samples and between 10 and 19 mitotic events in 5/16 (31.3%) cases. Mean Ki-67 expression was 2.39 ± 2.48%. FISS characterized as fibrosarcomas presented longer overall survival (median 545 days) than other histological subtypes (median 130.5 days) [P = 0.01].Discussion: Patients with FISS generally present with larger nodules than those with sarcomas not associated to injections, suggesting a challenge for pet owners to note subcutaneous tumors in the interscapular region, in addition to the aggressive biological behavior of FISS. The influence of size on prognosis remains controversial. An association between histologic grade and the development of metastasis has been observed, with patients with grade III FISS associated with an increase in the metastatic rate. The present study did not find a correlation between overall survival and histologic grade. A positive correlation between the presence of giant multinucleated cells and tumor grade has been observed.Despite the absence of such correlation in the present study, possibly due to a small sample, a trend for higher frequency of giant cells in advanced histologic grade was observed. Cox-2 expression in 81.75% and overexpression in 18.75% of our samples contrasts with the 64% Cox-2 expression and the absence of Cox-2 expression found by other authors. A positive moderate correlation between cellularity and Cox-2 expression was also observed, while another study did not find a correlation of Cox-2 expression with tumor grade, recurrence rates or overall survival. Cox metabolites such as prostaglandins can enhance cellular proliferation, inhibit apoptosis, induce angiogenesis, alter cellular adherence to facilitate metastatic development and inhibit immune surveillance. In the present study, no correlation was found between Cox-2 and angiogenesis in FISS. Our findings demonstrated low immunolabeling for Ki-67. A previous study analyzed 52 samples of FISS, 51% of them considered grade III, with a mean Ki-67 labeling of 14%. The lower Ki-67 staining in the samples of the present study may be related to the lower number of samples of grade III FISS or to a difference in the studied population. Fibrosarcomas are associated with better prognosis than other histological subtypes. Furthermore, malignant peripheral nerve sheath tumors were diagnosed as a possible histological subtype of FISS

Cyclooxygenase-2 expression in epithelial neoplasms and its relevance as a targeted therapy in dogs

ABSTRACT: Targeted therapy of neoplasms is an emergent approach in human and veterinary medicine. Cyclooxygenase (COX) is a class of catalytic enzymes related to the formation of inflammatory mediators. COX-2 is expressed constitutively in a few body tissues, but it may be induced in specific pathophysiologic conditions, such as cancer. COX-2 expression in neoplams may be considered a potential predictive factor, due to the possible association of selective COX-2 inhibitors in adjuvant treatments. This scientific communication has the objective to report COX-2 expression in seven neoplasms of dogs and the usage of adjuvant treatment with COX-2 selective inhibitors as an effective and feasible option in cancer treatment

Treatment of Canine Oral Melanoma with Adjuvant Chemotherapy and Immunotherapy

Background: Melanoma is the most frequent cancer in the canine oral cavity. It shows an aggressive behavior, characterized by rapid and invasive growth and high metastatic potential. Metastasis is seen in more than 80% of dogs at time of death. Adjuvant therapy should be recommended because of potential recurrence and metastasis. Oral melanoma has a poor prognosis even when adjuvant treatments are used. There are some treatment options, but the high death rate due to the disease is still a challenge. The aim of this study was to assess the overall survival of dogs diagnosed with oral melanoma and treated with adjuvant chemotherapy and immunotherapy. Materials, Methods & Results:A retrospective analysis was carried out in 20 dogs with oral melanocytic or amelanocytic melanomas. Cases were staged according to a modified World Health Organization clinical staging system for canine oral malignant melanoma. Tumor size (T1: < 2 cm; T2: 2 - 4 cm; T3: > 4 cm), regional metastasis (N0: no metastasis; N1: metastasis) and presence of distant metastasis (M0: no metastasis; M1: metastasis) are evaluated. Then, cases were divided into 4 stages: I (T1 N0 M0), II (T2 N0 M0), III (T3 N0-1 M0, Tx N1 M0) and IV (Tx Nx M1). Diagnoses were confirmed with histopathological exam and immunohistochemistry (IHC) when necessary. In poorly differentiated neoplasms, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Animals were divided into 2 groups: dogs submitted to surgery alone were included in group 1 (G1); dogs submitted to surgery associated with adjuvant chemotherapy with four 21-day cycles of carboplatin (300 mg/m2) and immunotherapy with six 7-day cycles of interferon-α (3 x 106 IU/m2) were included in group 2 (G2). Twenty dogs diagnosed with oral melanoma were evaluated: 3 were included in G1 and 17 in G2. Considering clinical staging of the dogs: 7 stage II, 12 stage III and only 1 stage IV. There was no stage I patients. In poorly differentiated neoplasias, IHC was performed at the request of the submitting veterinarian using specific markers PNL-2 and Melan-A. Patient follow-up was obtained through the evaluation of patient records and telephone interviews with owners. The overall survival time (OS) was defined by the period (in days) between the date of surgical excision and the death caused by the disease. Median overall survival time was 86 days for animals in G1 and 894 days for animals in G2 (P = 0.01). Discussion: Carboplatin was considered an appropriate cytostatic drug to treat microscopic disease in oral melanoma. INF-α was chosen for immunotherapy in this study because it promotes immune system stimulation associated with an indirect antiproliferative effect on neoplastic cells. The association of INF-α and carboplatin resulted in a significant increase in overall survival, when compared to the literature, suggesting that association of chemotherapy and immunomodulation is an important strategy in the treatment of canine oral melanoma. Controlled prospective randomized trials are necessary to confirm the benefits of chemotherapy and immunotherapy association to treat canine oral melanoma. Adjuvant therapy with chemotherapy and immunotherapy was considered effective to increase overall survival and maintained quality of life of dogs diagnosed with oral melanoma

Electrochemotherapy treatment of oral extramedullary plasmacytoma of the tongue: a retrospective study of three dogs

<div><p>ABSTRACT: Extramedullary plasmacytomas (EPs) are responsible for 2.5% of neoplasms in dogs. They are solitary, smooth, elevated, pink or red nodules, of 1 to 2cm in diameter. Cutaneous and oral extramedullary plasmacytomas in dogs are usually benign tumors, treated with local therapies. Prognosis is generally good. Recurrence and metastatic rates are low. Electrochemotherapy is a local treatment that combines chemotherapy and electroporation and shows objective responses of 70% to 94% with few local and systemic side effects. This scientific communication has the objective to report treatment of three canine patients with oral extramedullary plasmacytoma. Nodules were located on the tongue and patients were submitted to one or two electrochemotherapy sessions, which preserved the tongue without mutilation and cured the patients.</p></div

Diferential Diagnosis between Esophageal Granuloma and Pulmonary Metastasis

Background: Spirocercosis is a parasitic infection caused by Spirocerca lupi. This pathology affects canid carnivores, especially domestic dogs. Early diagnosis has been proven challenging and most infected animals are diagnosed when disease is in advanced stage. Exams such as computed tomography scans or radiographs can aid in disease confirmation.Radiographic exam frequently reveals the presence of a mass located in mediastinal region, which can be erroneously diagnosed as pulmonary mass. The aim of this study was to report the differential diagnosis between paraesophageal granuloma, possibly due to spirocercosis, and pulmonary metastasis in a dog with a history of neurofibrosarcoma.Case: A 8 year-old male Cocker Spaniel dog, weighing 17.4 kg, was presented with anterior limb suspension and a recurrent nodule of 2.0 cm diameter, located on the main pad, with previous diagnosis of neurofibrosarcoma (malignant Schwannoma). Routine evaluation work-up included thoracic radiographs and abdominal ultrasound for clinical staging, electrocardiogram, complete blood count (CBC), coagulogram, renal and hepatic function tests, with results within the normal range for the species. The dog submitted to left anterior limb amputation due to recurrent neurofibrosarcoma in the carpal region. Histopathological exam confirmed recurrent neurofibrosarcoma without vascular invasion. Considering neoplasm biological behavior and clean surgical margins, only routine follow-up was established, with clinical exams. The dogwas presented to the Veterinary Hospital five months after surgical treatment and it was presented with fever, prostration, and history of vomiting. Radiographic exam showed a circumscribed mass in caudal mediastinal area. Computed tomography scan was performed to best evaluate the mass and the result was compatible with paraesophageal abscess. These findings were consistent with paraesophageal abscess with necrotic center caused by Spirocerca lupi; however, it was not possible to exclude the possibility of lymph node neoplasms, with necrotic center/secondary abscess. Coproparasitological test result was negative; however, considering the endemic aspect of spirocercosis, the dog was treated with Ivermectin was given orally, for 14 days, and complete remission was observed at the end of the treatment, without any significant side effects.Discussion: Spirocercosis has a worldwide dissemination, limited only by the presence of intermediate host. In endemic regions, prevalence in dogs may be 100%. Diagnosis may be challenging, especially in atypical cases and in patients with complications. Spirocercosis diagnosis may be achieved from therapeutic response in typical cases, with suggestiveradiographic and tomographic findings. Radiologic and tomographic findings in this case were similar to common spirocercosis findings. Follow up by a veterinary oncologist is of utmost importance; an unprepared veterinarian could indicate thoracotomy or even euthanasia. Even though coproparasitological exam was negative, the endemic aspect of spirocercosis in the area supported the decision for treatment and therapeutic diagnosis. Oncologic patients should be carefully evaluated,for not all pathologies they develop after a neoplasm diagnosis are related to cancer. Knowledge of disease biologic behavior is essential to make correct decisions regarding patient health status.Keywords: Spirocerca lupi, granulomas, neurofibrosarcoma

Tumor ósseo multilobulado em cães: aspectos clínicos, histológicos, imunohistoquímicos e sobrevida (relato de dois casos)

Background: Multilobular tumor of bone (MTB) is an unusual neoplasm with variable biologic behavior which originates primarily in bone tissues. Radiographs computed tomography (CT), and magnetic resonance imaging (MRI) are useful in diagnoses and surgical planning. Tumor removal with wide surgical margins is the treatment of choice. Immunohistochemistry has been shown as an important tool in veterinary oncology to define therapeutic and prognostic decisions. The goal of this study was to report 2 distinct cases of multilobular tumor of bone, their Cox-2 and Mib-1 immunohistochemical profile and its impact on overall survival. Case: Two bitches were presented at the Oncology Department of the Veterinary Hospital in the Veterinary School of Universidade Federal de Minas Gerais (UFMG). Both had a history of a progressive, painless, circumscribed, and firm facial mass. The 1st patient was a 8-year-old intact bitch mixed breed, weighing 50 kg, that presented a fast growing right infraorbital 3-cm mass, causing eye displacement. The 2nd patient was a 7-year-old spayed bitch Labrador retriever, weighing 28 kg, that presented a left temporal 8-cm mass. Neurologic examination of both bitches was normal. Skin over the nodules was strained, but with no ulceration. Radiographic exams of the head revealed lytic and proliferative bone reaction, with loss of cortical definition in both cases. These alterations were seen on the left zygomatic arch of the retrobulbar region, involving part of the mandible and of the nasal sinus lateral frontal bone in 1st patient, and on the right temporal process of the zygomatic bone in 2nd patient. The last one, also showed a granular solid mass with little contact with skull bones. Complete blood count, biochemistry profile, electrocardiogram, and 3-view thoracic radiographs were performed. Results were within normal ranges for the species and no signs of metastasis was seen on the radiographs. Location, size, and density of the mass, adjacent tissue compression, absence of cranial invasion, and lymph node size were rigorously evaluated with CT, allowing an individualized surgical planning to achieve complete mass removal and maintenance of the function of adjacent structures. Both animals were submitted to surgery. Both tumors were fixed on 10% neutral buffered formalin and sent to the Animal Pathology Department of UFMG for histopathological examination and margin assessment. Both tumors were diagnosed as grade I MTB. Tumor immunohistochemistry was performed to identify prognostic factors that could be used to better define therapeutic treatments and to try to clarify the discrepancy in disease progression between both tumors. The 1st patient expressed 20% of Mib-1 and was considered score 2 of Cox-2. The 2nd one expressed 5% of Mib-1 and was considered score 1 of Cox-2. Considering the diagnoses and histological characteristics of the tumors, it was decided for clinical follow-up of patients without additional therapeutic complementation. Even considering incomplete surgical margins in 2nd patient, adjuvant chemotherapy was not performed, due to low mitotic index and low histological grade. The 1st patient had an overall survival of 240 days, and death was due to recurrence and disease progression; and the 2nd did not show recurrence nor metastasis after 1200 days. Discussion:  Proper and individualized surgical planning and histopathological evaluation are extremely important to guide treatment decisions. However, immunohistochemistry can be important in MTB cases, to help define which patients should be submitted to surgery alone and which patients could be benefited from adjuvant chemotherapy. Keywords: MTB, Cox-2 and Mib-1 profile, neoplasm, tumor, oncology, canine, dog, bone tissues.                 Tumor ósseo multilobulado (TOM) é uma neoplasia incomum, com comportamento biológico variável, que se origina primariamente em tecidos ósseos. Radiografia, tomografia computadorizada (TC) e ressonância magnética (RM) são úteis para diagnóstico e planejamento cirúrgico. Exérese do tumor com margens cirúrgicas amplas é o tratamento de escolha. Imunohistoquímica tem se mostrado uma ferramenta importante na oncologia veterinária para ajudar a definir decisões terapêuticas e prognósticas. O objetivo deste trabalho foi relatar dois casos distintos de TOM, seu perfil imunohistoquímico de Cox-2 e Mib-1 e o impacto na sobrevida global.&nbsp; Dois cães com histórico de massa firmem, progressiva, indolor e circunscrita em região de face foram atendidos pelo departamento de oncologia do Hospital Veterinário da Universidade Federal de Minas Gerais (UFMG). Ambos tinham histórico de massa facial progressiva, indolor, circunscrita e firme. O primeiro paciente era uma cadela de 8 anos, 50 kg, sem raça definida, inteira, que apresentava uma massa infraorbitária direita de crescimento rápido de 3 cm, causando deslocamento ocular. O segundo paciente era um labrador retriever, castrado, de 7 anos, 28 kg, que apresentava uma massa temporal esquerda de 8 cm. O exame neurológico de ambos os animais não apresentou alterações. A pele sobre os nódulos estava tensa, mas sem ulceração. Exames radiográficos da cabeça mostraram reação óssea lítica e proliferativa, com perda da definição cortical em ambos os casos. Essas alterações foram observadas no arco zigomático esquerdo da região retro bulbar, envolvendo parte da mandíbula e do osso frontal lateral do seio nasal, no primeiro paciente, e no processo temporal direito do osso zigomático no segundo paciente, que também apresentou uma massa sólida granular com pouco contato com os ossos do crânio. Hemograma completo, perfil bioquímico, eletrocardiograma e radiografia torácica em três incidências foram realizados. Os resultados estavam dentro da normalidade para a espécie e nenhum sinal de metástase foi detectado nas radiografias. Localização, tamanho e densidade da massa, compressão do tecido adjacente, invasão craniana e tamanho dos linfonodos foram rigorosamente avaliados com TC, permitindo um planejamento cirúrgico individualizado para a remoção completa da massa e manutenção da função das estruturas adjacentes. Ambos os cães foram submetidos à cirurgia. Os tumores foram fixados em formalina tamponada neutra a 10% e encaminhados ao Departamento de Patologia Animal da UFMG para exame histopatológico e avaliação das margens. Ambos os tumores foram diagnosticados como MTB grau I. A imuno-histoquímica dos tumores foi realizada para identificar fatores prognósticos que pudessem ser usados ​​para definir melhor as condutas terapêuticas e tentar esclarecer a discrepância na progressão da doença entre os dois tumores. O primeiro paciente expressou 20% de Mib-1 e foi considerado escore 2 de Cox-2. O segundo expressou 5% de Mib-1 e foi considerado escore 1 de Cox-2. Considerando os diagnósticos e as características histológicas dos tumores, optou-se pelo acompanhamento clínico dos pacientes sem complementação terapêutica adicional. Mesmo considerando margens cirúrgicas incompletas no segundo paciente, não foi realizada quimioterapia adjuvante, devido ao baixo índice mitótico e baixo grau histológico.O primeiro paciente teve sobrevida global de 240 dias, sendo o óbito por recorrência e progressão da doença; e o segundo não apresentou recidiva nem metástase após 1200 dias. Planejamento cirúrgico adequado e individualizado e avaliação histológica são de extrema importância para guiar a escolha do tratamento. No entanto, a imunohistoquímica pode ser importante em casos de TOM, para ajudar a definir quais pacientes devem ser submetidos apenas a cirurgia e quais pacientes podem se beneficiar da associação com quimioterapia adjuvante

Tumor ósseo multilobulado em cães: aspectos clínicos, histológicos, imunohistoquímicos e sobrevida (relato de dois casos)

Background: Multilobular tumor of bone (MTB) is an unusual neoplasm with variable biologic behavior which originates primarily in bone tissues. Radiographs computed tomography (CT), and magnetic resonance imaging (MRI) are useful in diagnoses and surgical planning. Tumor removal with wide surgical margins is the treatment of choice. Immunohistochemistry has been shown as an important tool in veterinary oncology to define therapeutic and prognostic decisions. The goal of this study was to report 2 distinct cases of multilobular tumor of bone, their Cox-2 and Mib-1 immunohistochemical profile and its impact on overall survival. Case: Two bitches were presented at the Oncology Department of the Veterinary Hospital in the Veterinary School of Universidade Federal de Minas Gerais (UFMG). Both had a history of a progressive, painless, circumscribed, and firm facial mass. The 1st patient was a 8-year-old intact bitch mixed breed, weighing 50 kg, that presented a fast growing right infraorbital 3-cm mass, causing eye displacement. The 2nd patient was a 7-year-old spayed bitch Labrador retriever, weighing 28 kg, that presented a left temporal 8-cm mass. Neurologic examination of both bitches was normal. Skin over the nodules was strained, but with no ulceration. Radiographic exams of the head revealed lytic and proliferative bone reaction, with loss of cortical definition in both cases. These alterations were seen on the left zygomatic arch of the retrobulbar region, involving part of the mandible and of the nasal sinus lateral frontal bone in 1st patient, and on the right temporal process of the zygomatic bone in 2nd patient. The last one, also showed a granular solid mass with little contact with skull bones. Complete blood count, biochemistry profile, electrocardiogram, and 3-view thoracic radiographs were performed. Results were within normal ranges for the species and no signs of metastasis was seen on the radiographs. Location, size, and density of the mass, adjacent tissue compression, absence of cranial invasion, and lymph node size were rigorously evaluated with CT, allowing an individualized surgical planning to achieve complete mass removal and maintenance of the function of adjacent structures. Both animals were submitted to surgery. Both tumors were fixed on 10% neutral buffered formalin and sent to the Animal Pathology Department of UFMG for histopathological examination and margin assessment. Both tumors were diagnosed as grade I MTB. Tumor immunohistochemistry was performed to identify prognostic factors that could be used to better define therapeutic treatments and to try to clarify the discrepancy in disease progression between both tumors. The 1st patient expressed 20% of Mib-1 and was considered score 2 of Cox-2. The 2nd one expressed 5% of Mib-1 and was considered score 1 of Cox-2. Considering the diagnoses and histological characteristics of the tumors, it was decided for clinical follow-up of patients without additional therapeutic complementation. Even considering incomplete surgical margins in 2nd patient, adjuvant chemotherapy was not performed, due to low mitotic index and low histological grade. The 1st patient had an overall survival of 240 days, and death was due to recurrence and disease progression; and the 2nd did not show recurrence nor metastasis after 1200 days. Discussion:  Proper and individualized surgical planning and histopathological evaluation are extremely important to guide treatment decisions. However, immunohistochemistry can be important in MTB cases, to help define which patients should be submitted to surgery alone and which patients could be benefited from adjuvant chemotherapy. Keywords: MTB, Cox-2 and Mib-1 profile, neoplasm, tumor, oncology, canine, dog, bone tissues.                 Tumor ósseo multilobulado (TOM) é uma neoplasia incomum, com comportamento biológico variável, que se origina primariamente em tecidos ósseos. Radiografia, tomografia computadorizada (TC) e ressonância magnética (RM) são úteis para diagnóstico e planejamento cirúrgico. Exérese do tumor com margens cirúrgicas amplas é o tratamento de escolha. Imunohistoquímica tem se mostrado uma ferramenta importante na oncologia veterinária para ajudar a definir decisões terapêuticas e prognósticas. O objetivo deste trabalho foi relatar dois casos distintos de TOM, seu perfil imunohistoquímico de Cox-2 e Mib-1 e o impacto na sobrevida global.&nbsp; Dois cães com histórico de massa firmem, progressiva, indolor e circunscrita em região de face foram atendidos pelo departamento de oncologia do Hospital Veterinário da Universidade Federal de Minas Gerais (UFMG). Ambos tinham histórico de massa facial progressiva, indolor, circunscrita e firme. O primeiro paciente era uma cadela de 8 anos, 50 kg, sem raça definida, inteira, que apresentava uma massa infraorbitária direita de crescimento rápido de 3 cm, causando deslocamento ocular. O segundo paciente era um labrador retriever, castrado, de 7 anos, 28 kg, que apresentava uma massa temporal esquerda de 8 cm. O exame neurológico de ambos os animais não apresentou alterações. A pele sobre os nódulos estava tensa, mas sem ulceração. Exames radiográficos da cabeça mostraram reação óssea lítica e proliferativa, com perda da definição cortical em ambos os casos. Essas alterações foram observadas no arco zigomático esquerdo da região retro bulbar, envolvendo parte da mandíbula e do osso frontal lateral do seio nasal, no primeiro paciente, e no processo temporal direito do osso zigomático no segundo paciente, que também apresentou uma massa sólida granular com pouco contato com os ossos do crânio. Hemograma completo, perfil bioquímico, eletrocardiograma e radiografia torácica em três incidências foram realizados. Os resultados estavam dentro da normalidade para a espécie e nenhum sinal de metástase foi detectado nas radiografias. Localização, tamanho e densidade da massa, compressão do tecido adjacente, invasão craniana e tamanho dos linfonodos foram rigorosamente avaliados com TC, permitindo um planejamento cirúrgico individualizado para a remoção completa da massa e manutenção da função das estruturas adjacentes. Ambos os cães foram submetidos à cirurgia. Os tumores foram fixados em formalina tamponada neutra a 10% e encaminhados ao Departamento de Patologia Animal da UFMG para exame histopatológico e avaliação das margens. Ambos os tumores foram diagnosticados como MTB grau I. A imuno-histoquímica dos tumores foi realizada para identificar fatores prognósticos que pudessem ser usados ​​para definir melhor as condutas terapêuticas e tentar esclarecer a discrepância na progressão da doença entre os dois tumores. O primeiro paciente expressou 20% de Mib-1 e foi considerado escore 2 de Cox-2. O segundo expressou 5% de Mib-1 e foi considerado escore 1 de Cox-2. Considerando os diagnósticos e as características histológicas dos tumores, optou-se pelo acompanhamento clínico dos pacientes sem complementação terapêutica adicional. Mesmo considerando margens cirúrgicas incompletas no segundo paciente, não foi realizada quimioterapia adjuvante, devido ao baixo índice mitótico e baixo grau histológico.O primeiro paciente teve sobrevida global de 240 dias, sendo o óbito por recorrência e progressão da doença; e o segundo não apresentou recidiva nem metástase após 1200 dias. Planejamento cirúrgico adequado e individualizado e avaliação histológica são de extrema importância para guiar a escolha do tratamento. No entanto, a imunohistoquímica pode ser importante em casos de TOM, para ajudar a definir quais pacientes devem ser submetidos apenas a cirurgia e quais pacientes podem se beneficiar da associação com quimioterapia adjuvante