Metastatic Hepatocellular Carcinoma in Amazona aestiva

Background: Hepatocellular carcinoma is a primary malignant tumor of the liver tissue and its occurrence in birds is considered rare. The tumor can occur as a single mass leading to hepatomegaly, or as multiple nodules in the liver. In animals of the genus Amazona, only 1 case of metastatic hepatocellular carcinoma has been reported in the United States, therefore, little is known about its epidemiology and clinicopathological aspects in these species. In this context, the aim of this work was to describe a case of metastatic hepatocellular carcinoma in an Amazona aestiva.Case: A blue-fronted amazon parrot (Amazona aestiva) was referred to necropsy after being found dead in its enclosure. On examination, it presented cachectic body score. Examination of the coelomic cavity, revealed a serous translucent fluid and adhesions between the liver and peritoneum.A red mass restricted to the right hepatic lobe and raised to the capsular surface, interspersed with whitish and dark red multifocal areas was observed. When cut, this mass was soft, protruding, multilobulated, whitish and with a friable reddish center. Additionally, on the dorsal surface of the left lung lobe, therewas a rounded, well defined, whitish, and soft nodule. Microscopically, partial replacement of the hepatic parenchyma was observed by neoplastic proliferation of cuboidal epithelial cells, organized in mantle and supported by a scarce fibrovascular stroma. Cells have large, eosinophilic, well-delimited cytoplasm, with a central, oval nucleus, loose chromatin, and evident nucleolus. Moderate pleomorphism was characterized by anisocytosis, anisokaryosis, and aberrant nuclei. In the lung, a focally extensive mass with a pattern similar to that seen in the liver was observed. In the kidney, multifocal neoplastic emboli were noted. Liver immunohistochemistry was performed. Positive and negative controls were used to validate the reaction; however, there was no immunolabelling for the evaluated antibodies.Discussion: The histopathological characteristics observed in this study favored the diagnosis of hepatocellular carcinoma (HCC) with metastasis to kidney and lung. Primary liver tumors are rare in wild birds. In ducks, experimental studies have pointed aflatoxins and the duck hepatitis B virus as oncogenic agents, however, in birds of the genus Amazona, there are no studies that evaluate predisposing factors to the development of liver carcinoma. Macroscopically, hepatocellular carcinoma may present in massive, nodular or diffuse forms. In birds, the right lobe is the largest, which may suggest that this lobe is more prone to the development of HCC, as seen in the present case. The solid form, similar to that observed in this report, seems to be more commonly observed, as seen in the wild bird reports consulted. Metastases most often spread hematogenous, and in the present report there was metastasis to kidneys and lungs, which is a common feature for this neoplasm. In the present case, there was no labeling by any of the antibodies, perhaps because of their aggressiveness, associated with autolytic factors that prevent the labeling of antibodies, in addition to the specificity in the antibodyantigen relationship. This tumor must be differentiated from other liver tumors such as cholangiocarcinoma, and also the well-differentiated hepatocellular adenoma, in addition to non-neoplastic conditions. HCC should be considered as a differential diagnosis for Amazona aestiva found dead in the enclosure without previous clinical signs. This neoplasm is rare in Amazon parrots and reports should be encouraged in order to contribute to the understanding of the epidemiologicaland clinicopathological aspects of the tumor. Keywords: avian pathology, liver, neoplasm, immunohistochemistry. Título: Carcinoma Hepatocelular Metastático em Amazona aestiva Descritores: patologia aviária, fígado, neoplasma, imuno-histoquímica