Extrahepatic Cholangiocarcinoma in an adult Black Howler Monkey (Primates: Atelidae)

Over the past years, the number of neoplasm cases reported in nonhuman primates have considerably increased, with hepatocellular tumors reported in several species. Here a case report of extrahepatic cholangiocarcinoma in an adult male Black Howler Monkey (Alouatta caraya) is presented. The animal, kept as pet, was admitted at Veterinary Hospital presented clinical signs of cholestasis. After unsuccessful drug treatment, the animal was submitted to a cholecystoduodenostomy. During the surgical procedure, the hepatobiliary system was meticulously observed. The liver showed no macroscopic alterations, however, there was a solid mass throughout the common bile duct. Biopsy specimens were collected from the bile duct mass, liver and gallbladder for histological and immunohistochemical evaluations. Histological examination of the liver showed diffuse accentuated vacuolization and necrosis, besides hemosiderin accumulation inside hepatocytes. In the portal region, there was an accentuated proliferation of biliary ducts, which presented replete with bilirubin. Discrete neutrophilic inflammatory infiltrate and fibrosis were also observed. The bile duct mass showed a cellular proliferation of epithelial origin, confirmed by immunohistochemical analysis. The arrangement, characteristics and growth pattern of these cells revealed a malignant neoplasm. Despite the success of the procedure, the animal died hours later. Cholangiocarcinomas generally present high mortality rates, since its late clinical presentation make the treatments ineffective due to its large extensions at the time of diagnosis. The owner did not allow the necropsy, therefore the presence of other neoplasms and important organ alterations, which may be aggravated the patient's clinical condition, were not confirmed.