Lymphoma in Dogs: Understanding a Common Canine Cancer
Lymphoma is one of the most frequently diagnosed cancers in dogs, affecting thousands of pets each year. This disease targets lymphocytes, which are white blood cells that play a crucial role in the immune system. Because lymphocytes circulate throughout the body—in lymph nodes, spleen, bone marrow, liver, and blood—lymphoma is considered a systemic cancer, meaning it can impact multiple organs at once.
Types and Forms of Canine Lymphoma
Lymphoma isn’t just one disease. Veterinarians classify it based on where it appears in the body and what type of cell is involved. The main categories include:
- Multicentric lymphoma: The most common form, usually presenting as painless swelling of several lymph nodes.
- Mediastinal lymphoma: Affects structures within the chest, causing respiratory issues.
- Gastrointestinal (alimentary) lymphoma: Targets the digestive tract, leading to vomiting and diarrhea.
- Cutaneous lymphoma: Involves the skin, sometimes causing lesions or hair loss.
- Extranodal lymphoma: Occurs in single organs like the eyes or central nervous system.
Lymphomas are also divided by cell type: B-cell and T-cell varieties. This distinction matters because it influences prognosis and treatment response.
Recognizing Signs and Symptoms
The earliest warning sign for most dogs is enlarged lymph nodes. You might feel these under your dog’s jaw, in front of their shoulders, or behind their knees. Other symptoms depend on where the cancer develops:
- Lethargy or decreased energy
- Poor appetite or weight loss
- Vomiting or diarrhea (especially with gastrointestinal involvement)
- Coughing and trouble breathing (with mediastinal form)
- Facial or limb swelling
- Increased thirst and urination
- Skin lesions or patches of hair/color loss (cutaneous lymphoma)
If your dog shows any combination of these signs—especially swollen lymph nodes—it’s wise to schedule a veterinary exam promptly.
What Causes Lymphoma?
The exact cause remains unclear. Researchers believe both genetics and environment play roles. Some breeds—like Golden Retrievers, Boxers, Basset Hounds, and Cocker Spaniels—face higher risks. Exposure to certain chemicals or radiation may also contribute. Still, no single factor has been identified as responsible for most cases.
Diagnosing Lymphoma in Dogs
A veterinarian begins with a thorough physical exam to check for enlarged nodes or organ abnormalities. Definitive diagnosis requires sampling an affected node or tissue—usually by fine needle aspiration or biopsy—and having a pathologist examine the cells. Additional tests help determine how far the disease has spread:
- Bloodwork (CBC and chemistry panel)
- Urinalysis
- X-rays of chest/abdomen
- Abdominal ultrasound
- Bone marrow aspiration (if needed)
- Specialized tests (flow cytometry, immunohistochemistry) to identify cell type (B-cell vs T-cell)
Lymphoma Staging: How Far Has It Spread?
The stage reflects how extensively lymphoma has invaded the body:
- I: Single lymph node involved.
- II: Multiple nodes in one region (one side of diaphragm).
- III: Generalized node involvement on both sides of diaphragm.
- IV: Spread to liver/spleen.
- V: Involvement of bone marrow, blood, or other organs (eyes/skin/CNS).
A substage indicates whether your dog feels ill (b: symptomatic; a: asymptomatic). Prognosis worsens with higher stage/substage b disease.
Treatment Options for Canine Lymphoma
Chemotherapy remains the gold standard because lymphoma affects many parts of the body. The most effective protocol is called CHOP—a combination of cyclophosphamide, doxorubicin, vincristine, and prednisone—which sends most dogs into remission for months to over a year. Other options include COP protocols (without doxorubicin), single-agent drugs like doxorubicin or lomustine (CCNU), corticosteroids alone (prednisone), radiation for localized tumors, or even bone marrow transplantation in rare cases.
- Chemotherapy side effects are usually mild: occasional vomiting/diarrhea or reduced appetite; serious complications are uncommon.
- Certain breeds may lose fur during treatment.
If chemotherapy isn’t possible due to cost or other reasons, prednisone alone can shrink lymph nodes temporarily but doesn’t offer long-term control—and may make future chemotherapy less effective if started first.
Lifespan & Prognosis With Lymphoma
- No treatment: survival averages just one to two months after diagnosis.
- Chemotherapy: median survival is about ten to eighteen months for B-cell types; T-cell types typically have shorter remissions.
Cure is rare; most dogs eventually relapse as resistance develops with each round of therapy. When quality of life declines from symptoms or side effects that can’t be managed comfortably, euthanasia may be considered out of compassion for your pet’s well-being.
The Role of Genetics & Ongoing Research
Lymphoma risk varies among breeds due to genetic factors; ongoing studies aim to pinpoint these risks more precisely and develop new therapies that overcome drug resistance. Early detection through regular veterinary checkups—and prompt attention when you notice swollen glands or changes in appetite/energy—offers your dog the best chance at longer survival with good quality of life.
Main Takeaways About Lymphoma in Dogs
- Lymphoma accounts for up to twenty percent of canine cancers annually.
- B-cell lymphoma responds better than T-cell types; prognosis depends on stage/substage at diagnosis.
- Treatment should be tailored individually based on your dog’s health status and family goals.
