Canine Lymphoma: What Every Dog Owner Should Know (Updated 2025)

Canine lymphoma is a common cancer involving lymphocytes that usually presents as enlarged lymph nodes and systemic signs. Diagnosis uses cytology, staging tests, and immunophenotyping. Multi-agent chemotherapy offers the best chance for remission and longer survival. Causes are not proven, though some breeds appear predisposed. Regular checks and prompt veterinary evaluation improve treatment choices and outcomes.

What is canine lymphoma?

Canine lymphoma is a common cancer of a dog's lymphocytes (a type of white blood cell). It most often appears as enlarged peripheral lymph nodes (multicentric lymphoma), but can also affect the chest (mediastinal), gastrointestinal tract (alimentary), skin, or other organs.

Early signs to watch for

The most common sign is painless, swollen lymph nodes - usually under the jaw, behind the knees, or in the groin. Other frequent signs include weight loss, low energy, decreased appetite, increased thirst or urination, vomiting or diarrhea, and unexplained bleeding or infections.

Regularly feeling your dog's lymph nodes and scheduling routine exams with your veterinarian helps catch problems earlier.

How vets diagnose and stage it

Diagnosis usually starts with a fine-needle aspirate of an enlarged lymph node examined under a microscope (cytology). If needed, veterinarians may recommend a biopsy, blood tests (CBC, chemistry), urinalysis, chest X-rays, abdominal ultrasound, and bone marrow evaluation to stage the disease.

Modern staging often includes immunophenotyping (to determine whether the cancer cells are B-cell or T-cell) using flow cytometry or immunocytochemistry. B-cell lymphomas generally respond better to treatment than many T-cell types.

Causes and risk factors

The exact cause of lymphoma in dogs is unknown. Genetic predisposition exists in some breeds (for example, Boxers, Golden Retrievers, and Rottweilers), and researchers continue to study possible environmental links. No single environmental cause has been proven.

Treatment options

Chemotherapy is the standard treatment. Multi-agent protocols (often CHOP-based) produce the highest rates of complete remission and the longest median survival times. Single-agent therapies, corticosteroids (like prednisone), or palliative care are options when owners prefer less aggressive treatment.

Radiation can be effective for localized disease (for example, a single enlarged lymph node or a local tumor). Newer approaches such as targeted therapies and immunotherapy are under investigation in specialty centers.

Prognosis

Prognosis varies by disease stage, location, immunophenotype (B-cell vs. T-cell), and the treatment used. Without treatment, clinical decline often occurs over weeks to a few months. With appropriate multi-agent chemotherapy many dogs achieve remission and can have months to over a year of good-quality life; some live substantially longer. Your veterinarian can discuss expected outcomes based on your dog's specific diagnosis.

What owners can do now

Check your dog regularly for lumps. If you find swollen lymph nodes or notice persistent changes in appetite, weight, energy, or bowel habits, schedule a vet visit. Early diagnosis gives you more treatment choices and better information about prognosis.