Hepatocellular carcinomas in Vietnamese pot-bellied pigs (Sus scrofa)

Various neoplasms have been reported in Vietnamese pot-bellied pigs (Sus scrofa) with few reports of hepatocellular tumors. Twenty-two pot-bellied pigs diagnosed with hepatocellular carcinoma at necropsy over a 3-year period at one institution are described, representing 29% of the total pot-bellied pigs necropsied. The average age of affected pigs was 16.6 years with 15 males and 7 females. The most common clinical signs were decreased appetite (16/22) and weight loss (7/22). Grossly, the majority were massive tumors (13/22) with fewer nodular tumors (8/22) and 1 diffuse tumor. Massive tumors were typically multilobulated, very large, and encompassing 1 or more adjacent liver lobes, and were soft to firm and tan-yellow to orange-brown. Nodular tumors had multiple, 1-15 cm in diameter, discrete nodules in multiple liver lobes. Gross evidence of abscesses, necrosis, hemorrhage, or cysts associated with the tumor was occasionally described. Half of the cases had possible intrahepatic metastasis, and extrahepatic metastasis was identified in 3 cases, including to the hepatic lymph node (1/3), lung (2/3), spleen (1/3), and kidney (1/3). Histologically, all tumors had a trabecular or solid pattern, or a combination. An adenoid pattern was only identified in small regions of a few tumors. The neoplastic cells were relatively well-differentiated with moderate pleomorphism and a low mitotic index. Other histologic features within the tumors included intracellular glycogen or lipid accumulation, extramedullary hematopoiesis, foci of coagulative necrosis, and bile stasis. Aged pot-bellied pigs can be predisposed to hepatocellular carcinomas, which are locally aggressive and can metastasize within the liver and to other organs.