Combined hepatocellular and cholangiocellular carcinoma in a dog

A transitional type of combined hepatocellular and cholangiocellular carcin oma developed in a 12-year-old male Yorkshire terrier dog. The tumor was hi stologically composed of both hepatocellular carcinoma and cholangiocellula r carcinoma components, and both elements were closely intermingled. Intral uminal mucin accumulation in cytokeratin-positive tubular/glandular structu res was observed within the cholangiocellular carcinoma components and this feature was useful histological marker for a differential diagnosis betwee n combined hepatocellular and cholangiocellular carcinoma and a pseudogland ular type of hepatocellular carcinoma. This primary hepatic tumor is extrem ely ran in dogs.