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.

BackgroundMammary tumors are among the most frequent neoplasms in female dogs, but the strategies employed in animal treatment are limited. In human medicine, hormone manipulation is used in cancer therapy. Tamoxifen citrate is a selective inhibitor of oestrogen receptors and exerts a potent anti-oestrogen effect on the mammary gland. The aim of this study was to evaluate the adverse effects when exposing healthy female dogs to tamoxifen.MethodsTamoxifen was administered for 120 days at a dose of 0.5 or 0.8 mg/kg/day to either intact or spayed female dogs. The effects were assessed through clinical examination, haematology, serum biochemistry, ophthalmology and bone marrow aspirate examination. Ovariohysterectomy was performed and the uterus examined by histopathology.ResultsVulva oedema and purulent vaginal discharge developed with 10 days of tamoxifen exposure in all groups. Pyometra was diagnosed after around 90 days of exposure in intact females with frequencies increasing during the following 30 days of exposure. Up to 50% of dogs within the groups developed retinitis but none of the dogs had signs of reduced visual acuity. The prevalence of retinitis in each group was similar after 120 days of exposure. Haematological, biochemical and bone marrow changes were not observed. Due to the high risk of developing pyometra after prolonged exposure to tamoxifen, only spayed animals should be given this medication.ConclusionsA dose of 0.8 mg tamoxifen/kg body weight/day is recommended when treating tamoxifen-responsive canine mammary tumors. Due to the high risk of developing pyometra, ovariohysterectomy is recommended.

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The objective of this study was to determine the frequency of different categories of specific and general classification in canine cavitary effusions (CE), as well as their association with the underlying etiologies. The laboratorial and clinical data from 304 cases of canine CE were retrospectively assessed. In 32.9% (100 cases), at least one of the specific classification categories was established, with a subtotal predominance of neoplasia (42%), bacterial serositis (24%) and hemorrhage (16%). Neoplasia was confirmed by effusion cytology in 57.5% of the cases with histopathological confirmation. From the cases in which the specific classification was not obtained, 35.8% were classified as modified transudate, 30.4% as pure transudate, 21.1% % as exudate and 12.7% was not included in any general category. The most common causes of effusion among these cases were hypoproteinemia and/or hipoalbuminemia (HPHA) (25.8%), hepatopathy (22.5%), cardiac insufficiency (15.5%) and cytologically undetected cases of neoplasia (12.4%). In conclusion, HPHA, hepatopathy and neoplasia represents important etiologies for canine CE development. Classification of effusions, solely based on [TP] and TNCC, might be an inaccurate diagnostic tool of effusions. New laboratorial classification methods for canine CE should be researched. RESUMO O objetivo deste estudo foi determinar a frequência de diferentes categorias de classificação específica e geral em efusões cavitárias (EC) caninas, bem como sua associação com as etiologias subjacentes. Os dados laboratoriais e clínicos de 304 casos de EC canina foram avaliados retrospectivamente. Em 32,9% (100 casos), pelo menos uma das categorias específicas de classificação foi estabelecida, com predomínio subtotal de neoplasia (42%), serosite bacteriana (24%) e hemorragia (16%). A neoplasia foi confirmada pela citologia da efusão em 57,5% dos casos com confirmação histopatológica. Dos casos em que a classificação específica não foi obtida (204 casos), 35,8% foram classificados como transudato modificado, 30,4% como transudato puro, 21,1% como exsudato e 12,7% não foram incluídos em nenhuma categoria geral. As causas mais comuns de efusão nestes casos foram hipoproteinemia e/ou hipoalbuminemia (HPHA) (25,8%), hepatopatia (22,5%), insuficiência cardíaca (15,5%) e casos de neoplasia citologicamente não detectados (12,4%). Em conclusão, HPHA, hepatopatia e neoplasia representam importantes etiologias para o desenvolvimento da EC canina. A classificação geral de efusões, baseada exclusivamente em proteína e celularidade, pode ser uma ferramenta diagnóstica imprecisa. Novos métodos de classificação laboratorial para ECs caninas devem ser pesquisados. Palavras-chave: líquido cavitário, exsudato, peritoneal, pleural e transudato Recebido em 18 de abril de 2018 Aceito em 4 de junho de 2018