Epithelioid mesothelioma in a Crab-eating Fox - Cerdocyon thous (Linnaeus, 1766)

Mesothelioma is a malignant neoplasm considered rare, which has a mesothelial origin, affecting the cells that line body cavities and can affect humans, domestic animals and wild animals. In wild canids, it proves to be a rare find. The objective of the present study is to describe the macroscopic, histopathological and immunohistochemical aspects of a case of epithelioid mesothelioma in Cerdocyon thous, female, aged approximately 14 years and resident at the Center for Medicine and Research in Wild Animals of the Federal University of Mato Grosso. The individual presented with a severe clinical condition and rapid progression of signs. Despite the immediate start of supportive treatment, the animal died on the same day, being sent for necropsy. Macroscopically, multiple irregular, firm, reddish-white masses were observed in the omentum. In the histopathological analysis, it consisted of proliferation of neoplastic cells with a solid pattern, where the cells were predominantly rounded, with a slightly eosinophilic and normally broad cytoplasm, with a rounded, broad, normally vacuolated, basophilic and sometimes multiple nucleus. Anisocytosis and anisocariosis with mild to moderate intensity and mild cellular pleomorphism were also present. In addition, two to eight mitosis figures were observed in the field of higher magnification. The neoplastic population was supported by a delicate stroma of connective tissue that was sometimes thick and formed delicate septa. With this, the occurrence and first report of epithelioid mesothelioma in Cerdocyon thous is confirmed, contributing to the knowledge and description of a malignant neoplasm in a wild canid.