Hepatoma

The most common primary liver tumor is hepatocellular carcinoma, which arises from liver cells (hepatocytes) and tends to have a low rate of spread to other organs. Other primary liver tumors may originate from:

• bile ducts
• connective tissue
• blood vessels
• hormone-secreting (neuroendocrine) cells

Metastatic liver tumors are those that have spread to the liver from another organ. Tumors that metastasize to the liver from elsewhere in the body are more common than tumors that begin in the liver.

When the liver contains a single large mass—often termed a massive tumor—at least half of dogs with this presentation are diagnosed with hepatocellular carcinoma. Cats more commonly develop benign liver tumors than dogs. In cats, bile duct adenomas (biliary cystadenomas) make up more than half of liver tumors, but these are uncommon in dogs. Bile duct carcinomas are the most common malignant liver tumor in cats and the second most common liver tumor in dogs. Less common liver tumor types include:

• carcinoids
• various sarcomas
• myelolipomas

Clinical signs of liver tumors are usually nonspecific and often do not clearly indicate the liver as the main source of disease. About 75% of dogs and half of cats show illness signs, including:

• decreased appetite
• weight loss
• lethargy
• vomiting
• increased thirst
• increased urination
• abdominal enlargement due to fluid accumulation
• seizures

Some dogs and cats develop jaundice, which appears as yellow discoloration of the whites of the eyes, gums, inner ear flaps, and sparsely haired skin areas.

Figure 1. Abdominal x-ray of a dog with a large liver tumor (arrows outline the mass).

A primary care veterinarian may feel a liver mass during abdominal palpation. Additional diagnostics can include:

• blood testing (complete blood count, chemistry profile, coagulation profile, and urinalysis)
• abdominal radiographs
• abdominal ultrasound
• chest radiographs
• advanced imaging such as CT or MRI

Based on x-rays and/or ultrasound, the veterinarian may make a presumptive diagnosis of a liver tumor (Figure 1). Because liver surgery is complex and bleeding risk is significant, many primary care veterinarians refer patients to an ACVS board-certified veterinary surgeon for tumor removal and postoperative management.

Figure 2. A liver mass removed from a dog.

For primary liver tumors, the preferred treatment is surgical excision. The abdomen is opened with a large incision, and the affected liver portion is removed using surgical ligatures or a stapling device. Very large masses may require an additional incision along the rib cage to provide adequate access. Any other abnormal findings in the abdomen are also sampled when indicated.

Bleeding is a recognized risk in liver surgery. Surgeons commonly ensure that blood products are available in case transfusion becomes necessary during significant intraoperative bleeding. Another potential complication is incomplete removal of abnormal tissue, resulting in “dirty margins.” This can depend on the tumor’s location within the liver or which lobe is involved.

After surgery, pets are monitored in an intensive care unit and receive medications for pain control. Intravenous fluids and antibiotics may be administered for several days to support hydration and reduce infection risk. Daily blood tests may be performed to monitor for internal bleeding and organ dysfunction. If needed, blood or plasma transfusions may be given.

At home, pain relief and antibiotics may be required. If a pet will not eat its regular diet, a low-fat home-cooked diet may be offered. An Elizabethan collar should be used when the pet is not directly supervised to prevent licking at the incision; alternatively, a t-shirt can be used to protect the surgical site. A recheck appointment with the veterinary surgeon is typically scheduled about 10–14 days after surgery.

Long-term prognosis after liver tumor removal depends on tumor type, whether removal was complete, and whether spread (metastasis) is present. Surgical outcomes for hepatocellular carcinoma are generally very good: survival commonly exceeds 3.8 years, and metastasis occurs in less than 5% of cases. In cats, removal of resectable biliary cystadenomas is associated with a favorable prognosis and long survival. In contrast, surgery for bile duct carcinomas usually results in short survival times in both dogs and cats because of metastasis and tumor regrowth within the liver. Sarcomas and carcinoids carry a poor prognosis, since most have already metastasized at diagnosis.

Dogs with untreated primary liver tumors—particularly hepatocellular carcinoma—are 15 times more likely to die from tumor-related complications than dogs whose tumors have been surgically removed. Liver tumors are fragile and can rupture at any time, potentially causing life-threatening internal bleeding. A tumor may compress the main bile duct that carries bile into the intestine, leading to jaundice. It may also compress abdominal organs or major blood vessels, producing signs such as vomiting and abdominal enlargement from fluid. Rarely, liver tumors can secrete insulin-like substances, resulting in low blood sugar.

Postoperative ongoing bleeding, although reported in less than 2% of surgical patients, can still lead to death during the recovery period. Other possible complications include:

• infection
• twisting (torsion) of a liver lobe adjacent to the resected portion
• tumor regrowth within the liver
• spread of the tumor to other internal organs