What is canine lymphoma?
Lymphoma (also called lymphosarcoma) is a cancer affecting the lymphatic system: lymph nodes, spleen, liver and other lymphoid organs. It is one of the most common tumours in dogs, accounting for 7–24% of all canine cancers. It can occur at any age but is most common between 6 and 9 years.
Breeds with higher predisposition: Golden Retriever, Boxer, Bulldog, Basset Hound, Saint Bernard and Scottish Terrier. However, any dog can develop it.
Main types of canine lymphoma
Multicentric lymphoma (80% of cases)
Affects multiple lymph node groups simultaneously. It is the most common form and the one that responds best to treatment. The hallmark sign is firm, painless swelling of the lymph nodes in the neck, armpits, groin and behind the knees.
Alimentary (gastrointestinal) lymphoma
Affects the digestive tract. Symptoms include chronic vomiting, diarrhoea, weight loss and abdominal discomfort. Less common than multicentric lymphoma, with a poorer prognosis.
Mediastinal lymphoma
Affects the thymus and chest lymph nodes. Causes breathing difficulties, dry cough and, sometimes, pleural effusion. Common in Boxers.
Immunophenotype: B cell vs T cell
Regardless of location, lymphoma is classified as B-cell (approximately 60–80%) or T-cell type. B-cell lymphomas respond better to chemotherapy and have a longer median survival. This distinction is confirmed by immunohistochemistry or flow cytometry.
Warning signs: when to suspect lymphoma
- Visibly enlarged lymph nodes under the jaw, neck, armpits or groin — painless to the touch.
- Progressive lethargy and low energy.
- Loss of appetite and weight loss.
- Excessive thirst and urination (may indicate tumour-associated hypercalcaemia).
- Breathing difficulties or persistent cough.
- Chronic vomiting or diarrhoea without an obvious cause.
If your dog has olive-sized or larger lymph nodes for more than a week, see a vet without delay.
Diagnosis
- Fine-needle aspiration (FNA): cells are taken from the lymph node with a thin needle. Quick, minimally invasive, results in 24–48 hours.
- Biopsy: if FNA is inconclusive, a tissue sample is taken for full histological analysis.
- Staging: abdominal ultrasound, chest X-rays and bone marrow examination to determine disease extent (stages I–V).
- Immunohistochemistry: identifies B or T type, guiding prognosis and treatment planning.
Treatment options
CHOP chemotherapy
The gold standard is the CHOP protocol (cyclophosphamide, doxorubicin, vincristine and prednisone), given in cycles over 19–25 weeks. It achieves complete remission in 70–90% of dogs with multicentric B-cell lymphoma. Side effects exist but are generally manageable: mild nausea, minimal hair loss (far less than in humans) and moderate immunosuppression.
Single-agent doxorubicin
A simpler alternative with fewer vet visits. Lower remission rate and shorter duration, but valid in the right context.
Prednisone alone
Without chemotherapy, prednisone can temporarily shrink lymph nodes and improve quality of life for 4–8 weeks. Important: prior use of prednisone can create drug resistance and significantly reduce the effectiveness of CHOP if chosen later.
Quality of life during treatment
Many dogs on CHOP maintain excellent quality of life. They continue playing, eating well and enjoying their normal routines. Modern veterinary oncology prioritises animal welfare: if side effects are significant, doses are adjusted or treatment paused.
Key takeaways
- Lymphoma is one of the most common cancers in dogs — and it's treatable.
- Most common symptom: painless lymph node swelling in the neck, armpits or groin.
- With CHOP chemotherapy, most dogs achieve remission and live a median of 12–14 months.
- Early detection improves options: any unusual lump warrants a prompt vet visit.