Liver Tumors and Cancers in Dogs

Liver tumors account for 1% of tumors in dogs and are most common in dogs over 10 years old. The prognosis varies significantly depending on the type of tumor. Prompt diagnosis and treatment influences prognosis and dogs presenting with symptoms of a liver tumor require prompt veterinary attention.

Solitary hepatocellular carcinomas (HCC) are the most common tumor derived from the liver in dogs. These tumors often spread slowly and carry a good prognosis after surgical removal, with an average survival time of over 4 years. Most dogs that have HCC successfully removed die from other conditions. Other types of liver tumor tend to metastasize early and carry a poor prognosis. Early euthanasia is often appropriate.

Symptoms result from the effects of different types of liver tumor. Hepatocellular carcinoma (HCC) accounts for most liver tumors in dogs, and occurs in 3 forms:

• Massive - solitary, usually large mass, located in one liver lobe
• Nodular - smaller masses located in several liver lobes
• Diffuse - not identifiable as a single mass

Massive HCC is the most common liver tumor in dogs, and is prone to injury and bleeding. Some dogs present with signs of anemia, such as weakness and pale gums.

Nodular and diffuse HCC, as well as tumors of the bile ducts and gallbladder, spread widely within the liver and may spread around the body. These tumors sometimes result in symptoms of liver failure, such as seizures.

Some liver tumors are benign, meaning that they are not aggressive and unlikely to cause significant tissue damage or spread to other locations. These tumors generally cause no symptoms. In some cases, traumatic injury to the tumor causes bleeding, which may result in symptoms of anemia, similar to HCC. Examples of these tumors include:

• Hepatocellular adenomas
• Bile duct adenomas

The liver is also a common site for metastasis, or spread, of other types of cancers within the body. These cancers form tumors throughout the liver, and may cause symptoms similar to HCC.

The specific triggers for liver tumors are unknown and there are no risk factors that trigger tumor growth, other than age.

Symptoms of liver tumors are non-specific and often there are no clinical signs - many liver tumors are found while performing diagnostics for other conditions.

Diagnosis involves:

• Physical examination
• Blood work
• Testing of abdominal fluid
• Biopsy
• Aspiration of liver cells
• Diagnostic imaging

Treatment of liver tumors varies depending on the type of tumor, and includes treatments such as:

Surgery: Complete removal of the tumor where possible. In some cases, partial removal may help reduce bleeding from the tumor and abdominal pain.

Chemotherapy: to slow growth of the tumor. This does not significantly increase survival times.

Palliative care: includes liver-supporting supplements, pain medication, and steroids.

Prognosis varies depending on tumor type. Massive HCC is the most common type of liver tumor and, where surgical excision is possible, carries a good prognosis.

All other types of liver tumor carry a grave prognosis. Surgical removal of these tumors is difficult or even impossible due to their widespread nature, and most patients are euthanized.

Prevention of liver tumors is not possible, as the risk factors behind development of liver tumors, other than aging, are not known.

Liver tumors represent 1% of all tumors in dogs, making them uncommon.

Treatment of liver tumors vary depending on the type of tumor.

• Surgery
• Chemotherapy
• Palliative care