Intrahepatic Cholangiocarcinoma Identified in a Zoo-Housed Sandhill Crane (Grus canadensis): An Anatomopathological and Metagenomic Study

Abstract

Tumors in birds can be caused by a variety of factors such as species, age, sex, virus, chemicals, and environment. In particular, tumors are a major cause of death in long-lived birds such as parrots and zoo birds. A male sandhill crane that was bred for 8 years in a zoo was diagnosed with intrahepatic cholangiocarcinoma (ICC). At necropsy, the liver revealed a multinodular mass of variable colors, and severe cirrhosis and hemorrhages were present. Histologically, ICC was characterized by the presence of both types of ICC: small-duct type and large-duct type. Large-duct-type ICC was distinguished by the presence of multifocal biliary neoplasia, characterized by the diffuse papillary proliferation of columnar cells resembling large cholangiocytes. Small-duct-type ICC was characterized by the presence of non-mucin-producing cuboidal cells such as bile duct cells. In this case, no viral cause was identified from the metagenomic analysis and PCR of ICC; however, a contributing role of Cutibacterium sp. and E. coli identified from the metagenomics could not be excluded. This study is the first to describe the anatomopathological characteristics of ICC in the studied sandhill crane and attempts to determine its potential infectious etiology using metagenomics.

Keywords: birds; intrahepatic cholangiocarcinoma; metagenomics; neoplasm; sandhill crane.

Figure 1

Gross lesions of liver carcinoma. (A) Carcass of sandhill crane, (B) ascites (asterisk) retained in the coelomic cavity and masses of pleomorphic neoplasm, and (C) cholangiocarcinoma, right liver (blue arrow). Gizzard (yellow arrow), left liver (green arrow).

Figure 2

Histopathologic lesions of intrahepatic cholangiocarcinoma (ICC) in a sandhill crane. (A) Two compartments, one area with neoplastic cells similar to bile duct epithelium (a) and the other area with solid neoplastic columnar-cells containing only small luminal slits admixed with vacuolated hepatocytes and hemorrhages (b). (B) Large-duct-type ICC characterized by the mucin-producing papillary tumors developed through diffuse papillary proliferation of bile duct cells. (C) Moderately differentiated small-duct-type ICC is prominent, with irregular ductular patterns of neoplastic cells (arrows) that infiltrate the adjacent hepatic parenchyma. Fibrin deposition, severe hemorrhage, and hemosiderosis are shown. (D) Small-duct-type ICC that is composed of non-mucin-producing cuboidal cells, such as bile ducts (b) with hyperchromatic nuclei and condensed cytoplasm and deposition of fibrin between tumor cells (c), replacing normal hepatocytes (a). (E) A higher-magnification image showing large-duct-type ICC that is composed of columnar and mucin-producing cells characterized by large nuclei and abundant cytoplasm (a), compared to small-duct-type ICC (b). Original magnification: 40× for (A), 200× for (B,C), and 400× for (D,E).