Wondering about canine lymphoma symptoms? — Stage-by-stage progression and lymph node swelling check method

Oncology/CancerQ&AMeongsiljang Veterinary Advisory Board

Canine lymphoma is a malignant tumor of the lymphatic system, with swollen lymph nodes being the most common sign. We’ve put together a pet-owner-friendly guide covering the four types, five stages of progression, a self-check method for lymph nodes, and CHOP chemotherapy.

What is canine lymphoma?

A pet owner gently touching the lymph node area under their dog’s jaw while the dog is on the examination table at the veterinary clinic.

Canine lymphoma is a malignant tumor of the lymphatic system and the most common hematopoietic cancer, characterized by the abnormal proliferation of lymphocytes in lymphoid tissues such as lymph nodes, the spleen, and the liver. Early detection is truly crucial. If you notice sudden, painless, firm enlargement of the submandibular, prescapular, or popliteal lymph nodes, please visit a veterinary clinic as soon as possible. The risk of developing lymphoma increases with age, and textbooks report a higher predisposition in Boxers, Bernese Mountain Dogs, Bullmastiffs, Doberman Pinschers, Golden Retrievers, and Rottweilers.

Causes and risk factors for lymphoma

The exact cause of lymphoma remains unknown. However, it is believed to be associated with genetic predisposition, exposure to environmental carcinogens (such as herbicides), and chronic immune suppression or stimulation. That said, no single factor has been proven to have a strong causal link. According to veterinary internal medicine textbooks, the following risk factors have been reported: - Breed predisposition: A higher incidence has been reported in Boxers, Bernese Mountain Dogs, Bullmastiffs, Doberman Pinschers, Golden Retrievers, and Rottweilers. - Age: The risk generally increases with age, particularly in middle-aged and older dogs. - Environmental factors: Exposure to environments with frequent herbicide use has been discussed as a potential risk factor. - Immune dysfunction: Associations have also been reported in cases of long-term immune suppression.

Four types of canine lymphoma

Canine lymphoma is broadly categorized into four types based on the site of origin. The most common is multicentric lymphoma, which is the most frequently occurring form in dogs. - Multicentric: This is the most common form, characterized by generalized swelling of peripheral lymph nodes along with involvement of the spleen and liver. - Mediastinal (thymic): Enlargement of lymphoid tissue in the chest (thymus/mediastinum) can lead to difficulty breathing and coughing. - Alimentary: Involvement of gastrointestinal lymphoid tissue results in vomiting, diarrhea, and weight loss. - Extranodal: Occurs in specific non-lymph node sites such as the skin, eyes, central nervous system, and kidneys.

WHO clinical staging of lymphoma progression (5 stages)

Item	Stage 1	Stage 2	Stage 3	Stage 4	Stage 5
Extent of Involvement	A single lymph node or one organ (excluding bone marrow)	Two or more lymph nodes on one side of the body	Multiple lymph nodes throughout the body (generalized)	Stage 3 + liver/spleen involvement	Bone marrow involvement (± other organs)
Key Feature	Localized to one site	Confined to one side of the body	Spread to systemic lymph nodes	Progressed to organs such as liver and spleen	Progressed to the bone marrow
Changes the Owner Sees	Almost none	Mild lymph node swelling	Clear swelling of lymph nodes in multiple places	May be accompanied by appetite/weight changes	Possible systemic symptoms such as anemia and reduced energy
WHO Substage	a: no systemic symptoms / b: systemic symptoms present	a / b	a / b	a / b	a / b

WHO clinical stages are divided by the extent of involvement (lymph nodes → liver/spleen → bone marrow), and each stage is subdivided into substages a and b according to the presence or absence of systemic symptoms. Clinical stage, anatomical site, and immunophenotype (B-cell, T-cell) affect treatment and prognosis. Figures for the diagnosis rate or survival time per stage are not confirmed by the provided textbook excerpts, so they are not indicated.

Five places to check for lymph node swelling at home

There are five pairs of lymph nodes on a dog’s body that owners can feel directly. - Submandibular lymph nodes: Located on the inner side of the lower jaw, next to the salivary glands. Normal size is about that of a soybean to a quail egg. - Prescapular lymph nodes: Found on both sides of the chest, just in front of the shoulder blades. - Axillary lymph nodes: Situated deep within the inner part of the front legs, making them difficult to palpate. - Inguinal lymph nodes: Located in the groin area on the inner side of the hind legs. - Popliteal lymph nodes: Positioned above the knee on the back side of the hind legs. If there is a noticeable difference in size between the two sides, or if they feel hard and immobile, seek veterinary care immediately.

The owner gently palpating the puppy’s submandibular lymph nodes with their fingers to check their size.

Go to the vet within 24 hours if you see these signs

Seek prompt veterinary care if you notice any of the following signs. Multicentric lymphoma can progress rapidly, and enlarged lymph nodes may lead to difficulty breathing. These warning signs include: persistent difficulty breathing or coughing for more than 24 hours (suggestive of mediastinal lymphoma); sudden loss of appetite and rapid weight loss; vomiting or diarrhea lasting more than three days; pale gums and lethargy; and both sides of the lymph nodes enlarging quickly and feeling firm. Do not delay—have your pet evaluated at a veterinary clinic within 24 hours if you observe any of these symptoms.

Diagnostic tests performed at the vet

A definitive diagnosis of lymphoma is made through lymph node aspiration or biopsy. Initially, a fine-needle aspiration (FNA) cytology test is performed by inserting a thin needle into the swollen lymph node to extract cells. If the results are inconclusive, an excisional biopsy is conducted to remove part of the lymph node. Additionally, blood tests, chest X-rays, abdominal ultrasounds, and, if necessary, bone marrow examinations are used to check for involvement of other organs. Immunophenotyping is also performed to distinguish between B-cell and T-cell types. Confirming the immunophenotype is crucial because it influences treatment options and prognosis depending on the type.

Treatment — CHOP chemotherapy protocol

The standard treatment for canine lymphoma is multi-agent chemotherapy, which uses several drugs in combination. The most widely used protocol is the CHOP regimen, combining cyclophosphamide, doxorubicin, vincristine, and prednisolone. Your veterinarian will determine the appropriate drug dosages and schedule based on your dog’s weight, liver function, and bone marrow status, while also managing potential side effects on the blood and digestive system. Special caution is needed for breeds with MDR1 gene mutations, such as Collies and Shetland Sheepdogs, as they may be sensitive to drugs like doxorubicin and vinca alkaloids. If chemotherapy is not pursued, prednisolone can provide temporary symptom relief, but the response is typically short-lived.

A dog receiving intravenous chemotherapy alongside its owner at a veterinary oncology hospital.

Precautions for owners during treatment

For 1 to 3 days after chemotherapy, some of the medication may be excreted in your dog’s urine and feces. Wear disposable gloves when handling waste, flush the toilet twice, or double-bag it in plastic before disposal. Pregnant family members or those with weakened immune systems should avoid direct contact. If loss of appetite or vomiting persists for more than 24 hours, contact your veterinarian immediately.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently asked questions

Is canine lymphoma curable?

The goal for treating canine lymphoma is long-term remission (the disappearance of symptoms) rather than a complete cure. Many dogs achieve remission with standard multi-agent chemotherapy (CHOP-based protocols), but relapses are not uncommon. Even after a relapse, additional remission can be attempted with salvage (second-line) chemotherapy, so it’s best to consult your veterinarian to develop a tailored treatment plan.

How much does cancer treatment typically cost?

The CHOP protocol typically costs between $4,000 to $11,000 for a 19- to 25-week course. However, the final cost can vary significantly depending on medication prices, the frequency of diagnostic tests, and the tier of the veterinary hospital. It is advisable to consult with a veterinary oncology specialist early in the diagnostic process to receive a detailed cost estimate.

How long can my pet live without undergoing cancer treatment?

Without treatment, the disease can progress rapidly, shortening the pet’s life span. Using prednisolone (a steroid) alone may provide temporary symptom relief, but its effectiveness tends to wane over time, reducing its anticancer benefits. Even if you opt for palliative care only, always consult your veterinarian for proper management of pain and vomiting.

How should I manage my pet’s diet?

During cancer treatment, dietary management focuses on providing sufficient high-quality protein to maintain body weight and muscle mass. However, there is limited evidence that specific nutrient ratios or prescription diets can treat lymphoma itself, so any changes to your dog’s diet should always be discussed with your veterinarian to ensure they are appropriate for your dog’s individual condition.

Does swollen lymph nodes always mean lymphoma?

Not necessarily. Benign causes such as bacterial or viral infections, periodontal (gum) disease, and reactive lymph node hyperplasia are actually more common. However, if both lymph nodes swell simultaneously, are painless, and feel firm, the likelihood of lymphoma increases. To make an accurate distinction, diagnostic tests such as fine-needle aspiration cytology are required, so a veterinary examination is essential.

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References

[1] Schaer M, Gaschen FP, Clinical Medicine of the Dog and Cat, 4th Edition, Chapter on Hematopoietic Tumors, CRC Press, 2024

[2] Robinson NJ et al., 100 Top Consultations in Small Animal General Practice, Chapter 83 Lymphoma Chemotherapy Protocols, Wiley-Blackwell, 2014

[3] Vail DM, Thamm DH, Liptak JM, Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition, Elsevier, 2019