Hepatocellular Carcinoma in a Free-Ranging Three-Toed Sloth (Bradypus variegatus)

SIMPLE SUMMARY: Monitoring diseases and lesions in free-ranging and captive wild animals is important for biodiversity conservation and for understanding factors that can impact not only animal health but also human and environmental health. Here, we report for the first time a case of liver cancer in a free-ranging three-toed sloth (Bradypus variegatus) and describe the gross, microscopic, and immunohistochemical features of the lesion. The tumor was identified during the necropsy of a three-toed sloth that had to be euthanized due to serious consequences of an accident in the electrical network. Despite not being related to the cause of death of the animal, the type of tumor observed, a hepatocellular carcinoma (HCC), is one of the most frequent hepatic neoplasms in the liver of humans and domestic animals. ABSTRACT: The increasing interest of tumors in wildlife is important for biodiversity conservation and for monitoring environmental agents and/or contaminants with potential impact on human health. Here we described the occurrence of hepatocellular carcinoma (HCC) in noncirrhotic liver of a free-ranging three-toed sloth (Bradypus variegatus) from the Atlantic Forest biome in Brazil. The HCC showed a moderate mononuclear inflammatory infiltrate within the tumor tissue but with no inflammation and fibrosis in the adjacent liver tissue. Upon immunohistochemistry, neoplastic cells were diffusely positive for HepPar-1 and glutamine-synthetase presenting an irregular and random immunostaining pattern; β-catenin was positive in the cytoplasmic membrane of malignant hepatocytes; and cytokeratin 19 immunostaining was restricted to bile duct epithelial cells. The liver tissue was negative for HBV-like and HCV-like viruses assessed by molecular tests. The potential similarity of pathogenesis may reinforce the need for research on environmental and/or infectious agents associated with HCC that may contribute to the understanding of cancer in wildlife.