Hepatic Neoplasia

• Primary hepatic tumours are rare (less than 1.5% of all canine tumours and 1.0-2.9% of all feline tumours) * However, the liver is a common site of metastatic tumours due to the rich blood supply (hapatic portal vein and hepatic artery)
• In dogs, metastasis to the liver is 2.5 times more likely than primary neoplasia
• In cats, primary hepatobillary tumours are more frequent than metastatic tumours
• Malignant tumours are more common in dogs
• Benign tumours are more common in cats
• Malignant primary tumours include:
  • Hepatocellular carcinoma - the most common primary liver tumour in dogs and the second most common in cats
  • Cholangiocellular carcinoma
  • Gall bladder carcinoma
  • Haemangiosarcoma
  • Mast cell tumour
  • Hepatic carcinoids (neuroendocrine)
• Benign tumours include:
  • Hepatocellular adenoma (hepatoma)
  • Cholangiocellular adenoma
  • Gall bladder adenoma

Note: Distinction must be made between all hepatic tumours and benign nodular hyperplasia frequently observed in the older canine. The most significant primary tumours in the dog are hepatomas, hepatocellular and cholangiocellular carcinomas and hepatic carcinoids. Hepatocellular carcinomas and cholangiocarcinomas are the most significant in cats.

Diagnosis

Symptomatic in approximately 75% of dogs and 50% of cats, particularly if malignant.

Clinical signs

• Usually non-specific:
  • Weight loss
  • Inappetance
  • Lethargy
  • Polyuria-Polydipsia
  • Vomiting
  • Ascites
• Neurological Signs - seizures, ataxia and weakness occur less frequently. They may be due to metastasis to the central nervous system, hepatic encephalopathy or hypglycaemia which can occur as a paraneoplastic syndrome
• Icterus - Particularly in dogs with extrahepatic cholangiocarcinomas and diffuse carcinoids

Physical Examination

• Cranial abdominal mass - palpable in up to 75% of cats and dogs

Haematology and Biochemistry

• Usually non-specific. The following are frequently observed in dogs:
  • Mild non-regenerative anaemia - cause idiopathic, however, anaemia of chronic disease, inflammation, red blood cell sequestration and iron deficiency may play roles
  • Leukocytosis - resulting from the associated inflammation and necrosis with large liver masses
  • Thrombocytosis - potential causes include production of thrombopoietin as a parneoplastic syndrome, iron deficiency, inflammatory cytokines and anaemia
• Elevated hepatic enzymes - likely due to hepatocellular damage or biliary stasis though the level of enzyme increase is not proportional to severity of liver damage
• Hypoalbuminaemia
• Hyperglobulinaemia
• Hypoglycaemia
• Elevated pre- and postprandial bile acids

• The following have been observed in cats:
  • Azotaemia
  • Elevated hepatic enzymes
  • Elevated bilirubin

Plain Abdominal Radiography

A cranial abdominal mass is often observed with displacement of the stomach caudally and laterally with massive hepatic neoplasms. Occasionally mineralisation of the biliary tree is observed in dogs with cholangiocellular carcinoma. Three thoracic views should also be taken to assess lung metastasis although this is uncommon at the time of diagnosis.

Ultrasonography

Always recommended to evaluate the condition of surrounding structures. It also allows classification of the mass as massive, nodular or diffuse. Doppler techniques can also be utilised to assess the vascular structure of tumours. Guided fine-needle aspirates or core biopsies can also be taken at this time (a coagulation profile is hightly advised prior to liver biopsy due to risk of haemorrhage). If the lesion is solitary and massive surgical resection without preoperative biopsy is usually undertaken as diagnosis and treatemnt are accomplished in the singel procedure.

Advanced Imaging

CT and MRI are more sensitive in detecting small lesions and confirming the relationship of the mass with surrounding tissues and vasculature.

Hepatocellular Tumours (Hepatocellular carcinomas (HCC) and Hepatomas)

Signalment and Description

• HCC occurs more frequently in dogs and hepatomas more commonly in cats. Male dogs over 10 years old are the most frequently affected. Miniature schnauzers may have a breed predisposition.
• Regional lymph nodes, peritoneum and lungs are the most frequent sites of metastasis in dogs with nodular and diffuse HCC.
• Metastatic rate for dogs with massive HCC: 0-37%
• Metastatic rate for dogs with nodular and diffuse HCC: 93-100%
• Hepatomas are usually incidental findings and non-significant

Cholangiocellular Tumours (Bile duct carcinomas and adenomas)

Signalment and Description

• Bile duct carcinomas are the most common malignant hepatobillary tumours in cats and the second most frequent in dogs, particularly females
• Intrahepatic carcinomas are more frequent in dogs. In cats there have been reports of both equal levels of occurrence of intra-and extrahepatic tumours and of a a extrahepatic dominance.
• Bile duct carcinomas are aggressive with metastasis to particularly the regional lymph nodes and lungs frequently being observed in dogs and diffuse intraperitoneal metastasis and carcinomatosis being common in cats.
• Bile duct adenomas (also known as biliary or hepatobiliary cystadenomas) are common in cats, particularly males.
• Bile duct adenomas are non-significant unless they of sufficient size to compress surrounding soft tissue structures

Carcinoids (Neuroendocrine Tumours)

Signalment and Description

• Usually occur in younger animals compared with other primary hepatobiliary tumours.
• Primary tumours are aggressive and often affect more than one liver lobe and metastasise to most frequently the regional lymph nodes, the lungs and peritoneum.

Sarcomas (Haemangiosarcoma (HSA), Leiomyosarcoma, Fibrosarcoma)

Signalment and Description

• HSA is the most common hepatic sarcoma in cats
• Leiomyosarcoma is the most common hepatic sarcoma in dogs
• These tumours are aggressive and metastasis to the spleen and lungs is frequently observed.

Carcinogens and toxins for example nitrosamines can induce hepatic tumours in an experimental environment. Cholangiocellular carcinoma occurs more commonly in female cats