Although the cause of this disease is unknown, there is an age-related incidence of hepatocellular carcinoma in older dogs, and dysregulation of the tumor suppressor gene TGFbeta-r, suggesting a role of exposure to environmental or dietary carcinogens in the pathogenesis of this condition.
Hepatocellular carcinoma is the most common primary hepatic tumor in dogs. Canine HCC is classified into three morphologic types; massive, nodular and diffuse, and the most common pattern is a massive lesion that involves a single liver lobe.
Hematological analysis often shows mild to moderate nonregenerative anemia, elevated ALT, ALP, hyperalbuminemia and increased albumin/globulin ratio. Prothrombin and activated prothrombin times should also be evaluated to asses clotting function.
Radiographically, there is usually loss of intraperitoneal detail due to effusion or intraperitoneal seeding of the tumor. Hepatomegaly is also a common finding.
A definitive diagnosis requires histopathological examination of biopsied tissue. Cytological diagnosis is relatively easy when hepatocytes have prominent criteria of malignancy, but is problematic when hepatocytes have a relatively normal morphologic appearance. Common features of hepatocellular carcinomas that assist in a differentiation from hepatocellular hyperplasia or hepatic adenoma is the dissociation of hepatocytes, acinar or palisading arrangements of neoplastic cells, and the presence of naked nuclei and capillaries, together with mild anisocytosis, anisokaryosis and multinuclearity.
A differential diagnosis would include hepatic adenoma, cholecystitis, hepatitis, hepatic neuroendocrine tumor, bile duct carcinoma, liver flukes (especially Clonorchis sinensis), hepatic adenoma and secondary metastatic lymphoma.
Liver lobectomy is the recommended treatment, and the prognosis after surgical resection is good in dogs. However, the major complication following hepatic resection is hemorrhage in dogs with a massive HCC. Surgical resection of right-divisional hepatic tumors involving the caudal vena cava, in particular, have a risk of large hemorrhage as a result of injury to this vein. Generally speaking, dogs with left-sided tumors live significantly longer than dogs with right-sided tumors.
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