Multimetastatic Hepatocellular Carcinoma in a South American Sea Lion (Otaria flavescens; Shaw, 1800)

An 18-year-old captive born and neutered male South American sea lion (Otaria flavescens, Shaw 1800) presented with intermittent symptoms of disease of the digestive tract (anorexia, reduced activity, vomit, and diarrhea). Over the course of 12 days, severe leukocytosis, signs of liver damage, and anemia developed accompanied by rapid weight loss and physical deterioration. Ultrasonographic examination revealed hepatomegaly and reduction of liver vascularization with altered hepatic parenchyma along with ascites. Hemoculture analysis results were sterile and PCR tests from nasal, oral mucosa and fecal swabs ruled out a Mycobacterium infection. Treatment consisted of antibiotics, anti-inflammatories, analgesics, probiotics, vitamin supplementations, antitoxic and hepatoprotective medication, supportive fluid therapy, and nutrition. Medical condition of the animal did not improve despite the treatments, presenting severe apathy (almost comatose), jaundice, oral bleedings, and melena. Thus, humane euthanasia was performed. At necropsy, major lesions were seen in the liver, confirming the ultrasonographic findings. Histopathology revealed a poorly demarcated hepatic epithelial neoplasia, metastasized in the lungs, spleen, and lymph nodes. Also, the presence of a neoplastic nodule at the level of the parathyroid made it difficult to define the primary site of neoplasia. An immunohistochemical examination using a panel of antibodies (Pan Cytokeratin AE1/AE3, CK18, CK8, together with p-CEA, CD10, and Vimentin) was performed attempting the differential diagnosis of hepatocellular carcinoma from cholangiocarcinoma, and metastatic non hepatic carcinoma. This test revealed that the tumor was of primary hepatic origin and metastasized in various organs, including the parathyroid which does not represent an usual site of metastasis. To our knowledge this is the first case describing hepatocellular carcinoma with evidence of metastasis in the lungs and parathyroid gland in a South American sea lion.