Mast cell tumors (MCTs) are hematopoietic neoplasms composed of mast cells. It is highly common in dogs and is extremely important in the veterinary oncology field. It represents the third most common tumor subtype, and is the most common malignant skin tumor in dogs, corresponding to 11% of skin cancer cases. The objective of this critical review was to present the report of the 2nd Consensus meeting on the Diagnosis, Prognosis, and Treatment of Canine Cutaneous and Subcutaneous Mast Cell Tumors, which was organized by the Brazilian Association of Veterinary Oncology (ABROVET) in August 2021. The most recent information on cutaneous and subcutaneous mast cell tumors in dogs is presented and discussed.

The best surgical technique for the treatment of mammary tumors in female dogs has been exhaustively debated among the scientific community. Despite biological knowledge of these tumors, some authors have suggested aggressive procedures, without any clinical advantage. The aim of this study was to evaluate the influence of surgical procedure on the overall survival, disease-free interval and new lesion development interval in dogs with mammary tumors treated according to established prognostic factors. This prospective study included 143 intact female dogs that underwent surgery for mammary neoplasms and were followed up for about 738.5 days. Each animal represented a repetition. Each surgical technique represented a group: lumpectomy (P1), mammectomy (P2), regional mastectomy without cranial abdominal gland involvement (P3), regional mastectomy with cranial abdominal gland involvement (P4), and radical mastectomy (P5). Considering only the first surgical event, 84.6% of animals had more than one mammary tumor, and tumors were identified in two mammary chains in 52.5%. There was no difference in ipsilateral and contralateral tumor development when surgical techniques were compared. Only 33 dogs developed new lesions in remaining mammary tissue, without correlation with primary lesion. Surgical technique had no effect on the overall survival, diseasefree interval and new lesion development interval in patients on this study, which respected oncological surgery principles and established prognostic factors for mammary gland tumors in dogs.

A imuno-histoquímica pode ser aplicada na oncologia veterinária para a definição do imunofenótipo neoplásico, com possibilidades ilimitadas de utilização. A técnica baseia-se na identificação de antígenos "in situ", que podem apresentar valor prognóstico e terapêutico. A expressão de receptores de estrógeno e progesterona está diretamente relacionada ao melhor prognóstico para os neoplasmas mamários, enquanto a super-expressão do receptor KIT (CD117), proteínas Ki-67 (MIB-1), VEGF, CD31 e COX-2 podem ser associados à progressão tumoral para vários tipos histológicos. Essa associação possui valor preditivo em potencial, tendo em vista a possibilidade da utilização de bloqueadores específicos. Esta revisão tem como objetivo apresentar as possibilidades da utilização da imuno-histoquímica nos tumores de cães, visando à definição mais precisa do prognóstico e a indicação de tratamentos específicos para cada paciente.

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Background: Thymomas are epithelial neoplasms of the thymus, although lymphocyte infiltration is common. Histological features are not sufficient to define its biological behaviour, which is dependent of clinical criteria of invasiveness and resectability. Myasthenia gravis may happen as a paraneoplastic syndrome in up to 47% of canine thymomas. Thisarticle aims at reporting a case of thymoma associated with myasthenia gravis in a dog, emphasizing the morphological, phenotypical and therapeutical aspects.Case: A 7-year-old, male Labrador, was presented with a history of acute dyspnea and exercise intolerance. The physical examination revealed a “red-brick” mucousa, tachycardia and cardiac and pulmonar hypofonese. Chest radiographs revealed an area of increased radiopacity in the cranial mediastinum without a plane of separation to the heart. The eccodopplercardiogram exam identified a poorly delimited mass adjacent to the base of the heart, measuring 9.5x6.8cm. Computed tomographydemonstrated it as an expansive neoformation (9.5x6.5x7.8cm). Mass was removed through intercostal thoracotomy and the removed tissue was submitted to histopathology with a diagnosis compatible with type AB thymoma (mixed). Immunohistochemistry was positive for AE1/AE3 citokeratin in 90% of epithelial cells, confirming tumour origin. Tumour infiltrating lymphocytes were positive for CD79a (70%) and CD3 (20%). The proliferation index (Ki-67 imunolabeling) was 60%. About 45 days after surgery the patient was presented with generalized muscle weakness and regurgitation, with confirmed megaesophagus on chest X-ray. Treatment with pyridostigmine was initiated because of suspected myasthenia gravis, and complete remission of the neurological signs occurred within a month. A chemotherapeutic protocol with carboplatin wasthen instituted. After four sessions, a new thoracic radiograph revealed tumour recurrence in the cranial mediastinum. Therefore, metronomic chemotherapy was started sequentially with oral chlorambucil and firocoxib. Patient remained well for nine months when regurgitation and muscle weakness re-initiated, even with pyridostigmine treatment. New chestX-ray demonstrated increased tumour mass and the owner decided for euthanasia, resulting in a survival time of 368 days.Discussion: The prognosis of the thymoma depends on the histological type, clinical staging and presence of paraneoplastic syndromes. Due to the heterogeneity of the cases, there are not enough studies available to compare the animals submitted to different therapeutic modalities. In humans, when possible, and in the absence of metastases, complete surgical resection is the standard treatment followed by chemotherapy and/or adjuvant radiotherapy. In dogs, surgical resection of thymomasshould be considered, despite the invasiveness detected in imaging studies. The presence of paraneoplastic syndromes, such as myasthenia gravis, are commonly associated with worse prognosis, however, as evidenced in this case, pyridostigmine was useful in maintaining the neuromuscular function and patient´s quality of life, along with surgery and adjuvant chemotherapy, which probably contributed to the increase of the expectation of life. Further studies are necessary to evaluate the efficacy of adjuvant chemotherapy in maximum tolerated and metronomic dosage, for thymic neoplasms in dogs.Keywords: thymus, neoplasia, paraneoplastic syndrome, carboplatin, cyclophosphamide.