A six-year-old female Dachshund presented intense abdominal distension caused by hemorrhagic effusion. Cytological examination of the fluid was performed and suggested a carcinoma. The animal was submitted to exploratory laparotomy and histological examination of the substantially altered spleen revealed epithelioid mesothelioma. Owing to a poor prognosis, poor response to chemotherapy, and development of thoracic effusions that required daily drainages, the owners decided for euthanasia. At necropsy, besides a 600 mL of sera-hemorrhagic abdominal fluid, no abnormal gross finding was identified in the abdominal cavity. The thoracic cavity was also filled with approximately 200 mL of effusion with same features as those detected in the abdominal fluid. A few firm white-to-gray nodules, with sizes ranging from 0.1 to 0.3 cm, were found in the lungs and diaphragm. Samples of the nodules were stained for routine histopathology and submitted to immunohistochemistry (IHC) assays using the antibodies vimentin, PAN Cytokeratin, calretinin, and TTF-1. Histopathology and IHC findings confirmed the diagnosis of metastatic papillary mesothelioma.

RESUMO O melanoma é considerado neoplasia de células redondas, de origem em melanócitos e melanoblastos. É comumente encontrada em mucosa oral e globo ocular, sendo também comum metástases para linfonodos e pulmões. Este trabalho teve por objetivo relatar um caso de melanoma em cão com ocorrência de metástase em locais incomuns. Uma cadela, treze anos de idade, da raça Poodle foi encaminhada para avaliação clínica com nódulo cutâneo na altura do osso radio esquerdo. Após exame citológico diagnosticou-se melanoma e durante a necropsia observou-se metástases em vários tecidos como fígado, coração e sistema nervoso central. No exame microscópico notou-se proliferação de células redondas a alongadas, pouco diferenciadas, arranjadas em manto por vezes em feixes. As células neoplásicas apresentavam citoplasma escasso, e eosinofílico, com raras granulações de coloração marrom. O melanoma é uma neoplasia que pode apresentar metástases em locais incomuns, como fígado, coração e sistema nervoso central, além de linfonodos e pulmões, locais mais frequentemente relatados. PALAVRAS-CHAVE: canino, metástase, neoplasia MELANOMA WITH MULTIPLE METASTASIS IN DOG-CASE REPORT ABSTRACT Melanoma is considered a neoplasia of round cells, originating in melanocytes and melanoblasts. It is commonly found in the oral mucosa and eyeball, and also metastases to lymph nodes and lungs. This work aimed to report a case of melanoma in dogs with metastasis in unusual places. A 13-year-old Poodle dog was referred for clinical evaluation with a cutaneous nodule at the height of the left bone. After cytologic examination, melanoma was diagnosed and necropsy revealed metastases in various tissues such as liver, heart and central nervous system. Microscopic examination revealed proliferation of elongated, slightly differentiated round cells, arranged in mantle, sometimes in bundles. Neoplastic cells had scarce cytoplasm, and eosinophilic, with rare granulations of brown color. Melanoma is a neoplasm that can present metastases in unusual places, such as the liver, heart and central nervous system, as well as lymph nodes and lungs, most frequently reported sites.

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