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

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Abstract: An 18-year-old captive born and neutered male South American sea lion (Otaria flavescens; Shaw, 1800) presented with intermittent gastrointestinal signs of disease (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 results revealed no growth, and PCR tests from nasal, oral mucosa, and fecal swabs ruled out a Mycobacterium infection. Treatment consisted of antibiotics, anti-inflammatories, analgesics, probiotics, vitamin supplements, antitoxic and hepatoprotective medication, supportive fluid therapy, and nutritional support. Medical condition of the animal did not improve despite the treatments, presenting as severe apathy (almost comatose), jaundice, oral hemorrhage, and melena. Thus, humane euthanasia was performed. On necropsy, major lesions were seen in the liver, confirming the ultrasonographic findings. Histopathology revealed a poorly demarcated hepatic epithelial neoplasia, metastasized to the lungs, spleen, and lymph nodes. Also, the presence of another neoplastic nodule at the level of the parathyroid made it difficult to define the primary tumor site. An immunohistochemical examination using a panel of antibodies (pan cytokeratin AE1/AE3, cytokeratin 18 [CK18], and CK8, together with p-CEA, CD10, and vimentin) was used in an attempt to differentiate between hepatocellular carcinoma from cholangiocarcinoma and metastatic non-hepatic carcinoma. Results revealed that the tumor was of primary hepatic origin and metastasized to various organs, including the parathyroid which does not represent a usual site of metastasis. To our knowledge, this is the first case describing hepatocellular carcinoma with evidence of metastases to the lungs and parathyroid gland in a South American sea lion.
Key Words: hepatocellular carcinoma, lung metastasis, parathyroid gland metastasis, South American sea lion, Otaria flavescens
Page Numbers: 362-370

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