Liver Cancer (Hepatocellular Carcinoma) in Dogs

Primary liver cancer accounts for less than 1.5% of all tumors in dogs. The most common type of cancer to originate in the liver is hepatocellular carcinoma. This cancer is believed to form on stem cells in the liver and it can grow to be quite large. It is responsible for about 50% of the liver tumors found in dogs. In some cases, the tumor can be identified as a palpable mass in a dog’s stomach. Often dogs present the typical symptoms of liver disease, but some tumors can be non-symptomatic for quite some time. Eventually, the tumor will cause serious abdominal hemorrhage. This type of cancer is slow growing; however, left untreated, it will cause cell death and cirrhosis of the liver and eventually lead to end-stage liver disease. It can metastasize to other areas of the body, most commonly to other organs in the abdomen, but this is less likely than with more aggressive forms of cancer. Surgery is possible with many tumors, and dogs have a good chance of recovery as long as the entire mass is removed. More diffuse tumors, including several lobes or even the entire liver, are much harder to treat. Cancers on the left lobe usually have a better chance of being successfully removed. This type of cancer is more common in older dogs, around 10-12 years of age.

Cancers often spread to the liver with metastasis, but primary liver cancer is rare in dogs. The most common tumor to originate in the liver is hepatocellular carcinoma. This is a slowly developing cancer. Many cases are treatable with surgery, but it will depend on the type and location of the tumor.

Hepatocellular carcinoma is much easier to treat in the early stages. Take your dog to see a veterinarian if you notice any of the following symptoms.

• Decreased appetite
• Weight loss
• Lethargy 
• Abdominal distention
• Mass can be felt in the stomach
• Vomiting
• Excessive thirst
• Frequent urination
• Bloody diarrhea
• Jaundice
• Ascites (fluid in the abdomen)
• Gastrointestinal bleeding
• Ulcers
• Hepatic encephalopathy (disorientation, circling, aggression, seizures coma)

Types

Hepatocellular carcinomas are defined by the type of tumor they form.

• Massive – the cancer forms as a single, discrete mass; as the name implies, it can grow to be very large; sometimes there is one large mass and several smaller ones in a different part of the liver; these tumors are easier to remove since they form a distinct growth
• Nodular – the cancer forms several nodes or smaller masses;  nodes may be located on one or more lobes of the liver; these tumors still form a discrete mass, but they are more likely to metastasize and spread than massive tumors
• Diffuse – the cancer may involve the most of the liver; cancerous cells are not well differentiated from healthy cells, so they can be difficult to remove
• Hepatocellular adenoma – this is a non-cancerous tumor that is the benign form of hepatocellular carcinoma; large tumors can still be a problem if they rupture and bleed, or if they put pressure on other abdominal organs

It’s not known what causes liver cancer to form. It is less common in dogs under 9 years old, so age is a factor. Some studies have noted a higher rate of incidence in Miniature Schnauzers, and others have found more tendency to liver cancer among male dogs, but this hasn’t been widely confirmed. 

The veterinarian will examine your dog physically. If a mass is felt on the liver, this will be a good indication of a hepatocellular tumor. If your dog has symptoms of liver dysfunction, cancer may be suspected as the cause, based on age and the elimination of other factors. Blood and urine tests will indicate the degree of liver failure that is present and help to determine whether your dog is healthy enough for surgery. Some bloodwork may require fasting. Abnormal liver enzymes may suggest the presence of a tumor or even show the type of cancer, but bloodwork isn’t often conclusive. 

A definitive diagnosis will be based on magnetic imaging. Massive tumors are visible on an abdominal X-ray. Ultrasound can identify smaller more diffuse tumors and help to show metastasis. Ultrasound guided biopsies and aspirates may be needed to determine if the tissue is cancerous or benign. The veterinarian may need to evaluate the coagulation level in your dog’s blood before these tests, since tumors may hemorrhage during biopsy. Additional x-rays, ultrasound, or other magnetic imaging tests could be ordered to check for metastasis in other parts of the body.

The veterinarian will want to know your dog’s age and medical history, including any prior problems with the liver. A detailed description of the symptoms will also be helpful.

Treatment will depend on a veterinarian’s diagnoses. Surgery is the best option, but in some cases it may not be possible. Nodular or diffuse tumors can be difficult to operate on, and tumors with a high degree of hemorrhage may pose too big a risk. If your dog has symptoms of acute liver failure, he will not be healthy enough for surgery unless this condition can be stabilized.

The veterinarian will discuss the amount of risk involved with surgery. Your dog may need to stay in a veterinary hospital for a number of days after surgery for monitoring. The liver can regrow itself, so dogs can recover even if a large amount of the liver has to be removed, but the veterinarian will need to ensure the liver is functioning adequately before sending your dog home. Biopsies will be taken during surgery to check for metastasis in other parts of the liver. It’s likely the veterinarian will put your dog on a low protein, low sodium diet to avoid unnecessary stress on the liver.

Chemotherapy may be ordered for tumors that are inoperable or if metastasis was noted at the time of surgery. Chemotherapy drugs are administered by injection for approximately 3 or 4 weeks, or as long as the veterinarian thinks necessary. Each chemotherapy appointment will last at least 1 ½ hours for adequate testing and administration. Dogs don’t usually experience hair loss, but they can have quite severe gastrointestinal side effects.

Massive or benign tumors that are fully removed with surgery have a good prognosis. Many dogs don’t have recurrence and may live for a number of years after the operation. The veterinarian may recommend a long-term diet change. 

Dogs with inoperable tumors have a low chance of recovery. Chemotherapy can sometimes slow the progression of the cancer, but only for a matter of months. Symptoms may progress gradually since this is not an aggressive cancer, but they will eventually become severe. The chance of your dog’s recovery will be evaluated by a veterinarian upon diagnosis.