Hepatic Lymphoma in Dogs and Cats

TL;DR. Hepatic lymphoma is an uncommon liver cancer in dogs and cats that is usually secondary to lymphoma elsewhere in the body, requiring prompt veterinary diagnosis and chemotherapy.

Hepatic lymphoma affects the liver, a vital organ located in the front of the abdomen.

What is it?

Hepatic lymphoma, also scientifically known as malignant lymphoma of the liver or hepatic lymphosarcoma, is a form of cancer that affects the liver. Lymphoma itself is a malignancy of the lymphocytes, which are a type of white blood cell crucial to the immune system. When these cells become cancerous, they can infiltrate various organs. In the case of hepatic lymphoma, these malignant cells invade the liver tissue, disrupting its normal structure and vital functions.

This disease typically presents in one of two ways. Most commonly, it is secondary, meaning it has spread (metastasized) to the liver from another location. In dogs, this is usually a manifestation of multicentric lymphoma, where multiple lymph nodes and organs throughout the body are affected. In cats, it is frequently secondary to alimentary (gastrointestinal) lymphoma. Less commonly, hepatic lymphoma can occur as a primary tumor, meaning the cancer originated directly within the liver itself. Primary hepatic lymphoma is rare and behaves differently than the secondary form.

Because the liver is a powerhouse organ responsible for filtering toxins, processing nutrients, producing blood-clotting factors, and aiding digestion, any disease that compromises its tissue can have widespread effects on your pet's health. Understanding whether the lymphoma is primary or secondary is critical, as it directly dictates the treatment plan and your pet's overall outlook.

Causes & risk factors

The exact cause of hepatic lymphoma in dogs and cats remains largely unknown. Like most cancers, it is believed to arise from a complex combination of genetic mutations and environmental influences. In cats, historical links to viral infections like Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) exist, though the widespread use of vaccines has changed the landscape of feline lymphoma.

Certain breeds of both dogs and cats show a higher statistical predisposition to developing lymphoma, suggesting an underlying genetic component. In dogs, breeds such as the Golden Retriever, Boxer, English Cocker Spaniel, Basset Hound, Rottweiler, Shih Tzu, and Siberian Husky are more frequently diagnosed. Among cats, the Siamese cat is notably predisposed to developing lymphoma. While any mixed-breed or purebred animal can develop this condition, owners of these specific breeds should remain particularly vigilant about routine health screenings.

Signs to watch for

The clinical signs of hepatic lymphoma can be vague and mimic many other liver or metabolic diseases. In some cases, particularly in cats, there may be no outward signs at all in the early stages of the disease. A leading veterinary internal medicine textbook notes:

"A suspicion may be gained from the clinical findings, but given that more than half of affected cats have no clinical signs, the liver mass may be a serendipitous finding while the cat is being evaluated for another reason."

When symptoms do develop, they can range from mild, generalized illness to severe, acute crises.

Common Signs

• Lethargy: Your pet may seem unusually tired, reluctant to play, or sleep more than normal.
• Weight loss: Unexplained weight loss, even if the pet's appetite seems unchanged initially.
• Hepatomegaly: An enlarged liver, which a veterinarian can feel during a physical exam and may sometimes cause the abdomen to look slightly swollen or distended.
• Increased liver enzyme activity: This is a key finding detected on routine blood chemistry panels.

Occasional Signs

• Anorexia: A loss of appetite or complete refusal to eat.
• Vomiting: Frequent or intermittent vomiting as the liver's metabolic functions decline.
• Jaundice (Icterus): A yellowing of the whites of the eyes, gums, or skin, caused by a buildup of bilirubin in the bloodstream.
• Splenomegaly: An enlarged spleen, which often occurs alongside liver enlargement.
• Ascites (Peritoneal effusion): Fluid accumulation in the abdomen, leading to a bloated, "pot-bellied" appearance.
• Coagulopathy: Bleeding disorders or difficulty clotting, as the liver fails to produce essential clotting factors.

Abdominal ultrasound is a key tool used to visualize changes in the liver's texture.

How vets diagnose it

Diagnosing hepatic lymphoma requires a systematic approach, starting with routine blood work and progressing to advanced imaging and tissue sampling.

Your vet will begin with a physical examination, checking for signs of an enlarged liver or spleen, fluid in the abdomen, or yellowing of the gums. Initial blood tests typically include a complete blood count (CBC) and a biochemistry profile. On clinical pathology, high liver enzyme activity, elevated bile acid concentrations, mild anemia, and an increased white blood cell count (neutrophilia) are common but non-specific findings that point toward liver dysfunction.

Abdominal ultrasonography is a vital tool for visualizing the liver's architecture. However, ultrasound alone cannot provide a definitive diagnosis. As a leading veterinary internal medicine reference explains:

"...lymphoma) may show a diffuse change in echogenicity, or the liver may appear normal on ultrasonography. Important differential diagnoses for diffuse hepatic tumors are FIP, lipidosis, and amyloidosis."

To differentiate lymphoma from these other conditions, your vet must obtain a cellular or tissue sample. This can be done via Fine-Needle Aspiration (FNA) or a biopsy. FNA involves using a thin needle to collect cells for cytology. However, if there are large, fluid-filled, or highly vascular masses, your vet will proceed with caution. A diagnostic cytology reference warns:

"...FNA of larger cavitational liver masses should be avoided because of the risk for capsule rupture, hemorrhage, and potential tumor seeding."

Because of these risks, and because the liver is responsible for blood clotting, your vet will perform a hemostasis profile (clotting test) before attempting any invasive sampling. The absolute gold standard for a definitive diagnosis is histopathology, which requires a larger tissue sample obtained via a Tru-Cut biopsy needle (often ultrasound-guided) or surgical biopsy. This allows a pathologist to examine the structure of the tissue and confirm the presence of malignant lymphocytes.

Treatment options

Once a diagnosis of hepatic lymphoma is confirmed, treatment is aimed at slowing the progression of the disease and maintaining a high quality of life. Unlike some other localized liver tumors, surgery is rarely an option for hepatic lymphoma because the disease is typically diffuse throughout the liver or part of a systemic process.

First-Line Therapy: COP Chemotherapy Protocol

The primary treatment for hepatic lymphoma is combination chemotherapy. The most common first-line regimen is the COP protocol, which stands for:

• Cyclophosphamide: An alkylating agent that damages the DNA of cancer cells.
• Oncovin (Vincristine): A drug that prevents cancer cells from dividing.
• Prednisone: A corticosteroid that is directly toxic to cancerous lymphocytes and helps reduce inflammation.

Chemotherapy in pets is designed differently than in human medicine; the doses are tailored to minimize side effects while maximizing comfort and extending survival. Most pets tolerate the COP protocol well, experiencing only mild, temporary side effects like mild nausea or lethargy.

Supportive Care

Alongside chemotherapy, your vet will prescribe supportive therapies to protect the remaining healthy liver tissue. This may include liver-specific antioxidants (such as S-adenosylmethionine or silybin), anti-nausea medications, and dietary modifications to reduce the workload on the liver.

Prognosis

The prognosis for pets with hepatic lymphoma depends heavily on whether the disease is primary or secondary.

If the hepatic lymphoma is secondary to multicentric lymphoma in dogs, the prognosis is often very good to excellent regarding their initial response to chemotherapy. Many dogs achieve clinical remission, meaning the signs of cancer temporarily disappear, and they can enjoy a high quality of life for several months to over a year.

Conversely, if the pet has primary hepatic lymphoma, the outlook is significantly more guarded. Primary malignant liver tumors generally do not respond well to standard therapies. As noted in a prominent veterinary internal medicine textbook:

"The prognosis for diffuse and nodular hepatocellular carcinomas and other forms of primary malignant liver tumors is poor because there is no effective therapy. Radiation therapy is not effective because the liver cannot tolerate cumulative doses of radiation. Hepatic tumors also respond poorly to chemotherapy, likely partly because of the development of rapid drug resistance by neoplastic hepatoc"

Your veterinarian will help you understand your pet's specific staging and what to expect based on their individual diagnostic results.

Prevention

There is no known way to prevent hepatic lymphoma in dogs or cats. Because the exact triggers are unknown, preventive care focuses entirely on early detection.

Bringing your pet in for annual or bi-annual veterinary exams—especially as they enter their senior years—is the best defense. Routine wellness blood screens can detect early elevations in liver enzymes before your pet shows any outward signs of illness, allowing for a much faster diagnostic path and earlier intervention.

When to call your vet

You should contact your veterinarian if you notice any persistent changes in your pet's behavior, appetite, or weight.

Seek immediate emergency veterinary care if your pet exhibits any of the following red-flag symptoms:

• Extreme weakness, collapse, or inability to stand.
• Pale or white gums, which can indicate internal bleeding.
• Sudden, severe swelling of the abdomen.
• Yellowing of the eyes, gums, or skin (jaundice).
• Uncontrolled vomiting or complete refusal to eat for more than 24 hours.

For specific breeds

If you own a Golden Retriever, Boxer, English Cocker Spaniel, Basset Hound, Rottweiler, Shih Tzu, Siberian Husky, or a Siamese cat, it is important to be aware of their increased risk for lymphoma. While you cannot change their genetics, you can advocate for their health by requesting routine screening blood work and abdominal palpation during their regular veterinary checkups. Early detection is one of the most powerful tools available in veterinary oncology.

Sources

• Internal Medicine, 5th Edition, pages 586, 617.
• Cowell and Tyler's Diagnostic Cytology and Hematology of the Dog and Cat, 5th Edition, page 359.