Distribution of domestic cat hepatitis B virus in cholangiocarcinoma and non-neoplastic liver tissue.

Domestic cat hepatitis B virus (DCHBV), shares similarities with human hepatitis B virus (HBV) which is associated with liver disease. We report the first case of cholangiocarcinoma in a 17-year-old spayed female cat infected with DCHBV and positive for feline immunodeficiency virus. The patient presented with vomiting, anorexia, and an elevated globulin level. Ultrasonography revealed multiple hypoechoic hepatic lesions, and histopathology confirmed cholangiocarcinoma. The tumor exhibited CK7 positivity and HepPar-1 negativity, confirming biliary origin. Quantitative PCR detected DCHBV in the spleen and ascitic fluid, while immunohistochemistry and RNA in situ hybridization revealed viral antigen and mRNA in both tumor and non-tumor liver. The presence of a viral antigen and mRNA in neoplastic tissue suggests a potential role for DCHBV in hepatobiliary carcinogenesis.