Understanding Canine Lymphoma: Symptoms, Diagnosis & Treatment

What is canine lymphoma?

Canine lymphoma is one of the most common cancers in dogs. Because it involves the immune system, it can affect multiple organs at once. Sometimes it acts quickly and loudly; other times it moves slowly and hides behind vague signs like low energy or weight loss. Either way, the earlier you spot changes, the more options you’ll have.

Symptoms of lymphoma in dogs (what you can spot at home)

The most recognizable clue is enlarged lymph nodes . Run your fingers gently:

• Under the jaw (submandibular)

• In front of the shoulders (prescapular)

• Behind the knees (popliteal)

• In the groin and armpits (inguinal/axillary)

Other common changes include a drop in energy, decreased appetite, weight loss, drinking and peeing more, or tummy troubles (vomiting/diarrhea). Coughing or faster breathing can occur when lymphoma affects the chest. Scaly or plaque-like lesions suggest a skin form called cutaneous lymphoma. If you’re seeing a few of these together—and they’re not going away—book a visit. Want a quick refresher on early warning signs across cancers? Try our guide: Early Signs of Dog Cancer & At-Home Screening.

The main patterns vets look for

Multicentric lymphoma
The most common form. Multiple lymph nodes enlarge around the body at once. Dogs often feel well at first.

Alimentary (gastrointestinal) lymphoma
Affects the stomach and intestines. Think soft stool, vomiting, weight loss, and sometimes abdominal pain.

Mediastinal lymphoma
Lives in the chest near the thymus. Can cause cough, labored breathing, or fluid buildup.

Extranodal lymphoma
Shows up outside the usual lymph node areas—eyes, kidneys, central nervous system, and more.

Cutaneous lymphoma
Also called “epitheliotropic lymphoma” when it involves the skin’s surface. You might see scaly patches, plaques, or nodules that don’t heal.

No single pattern is “better” or “worse” on its own—location, subtype, and your dog’s overall health all matter.

What “T-cell” and “B-cell” mean—and why it matters

Lymphoma is also grouped by cell type: T-cell lymphoma or B-cell lymphoma . This is identified on lab testing (immunophenotyping/flow cytometry). Knowing the type helps your vet choose the best treatment plan and discuss prognosis in plain English.

When is it an emergency?

Call your vet or an emergency clinic now if you see:

• Fast or difficult breathing

• Pale or white gums

• Severe vomiting/diarrhea or refusal to drink

• Collapsing or extreme lethargy

• A swollen belly that seems painful

These can signal complications that need same-day care.

How vets diagnose lymphoma (step-by-step)

Exam & history. Your vet will feel lymph nodes, check temperature and hydration, and review recent changes in appetite, energy, and bathroom habits.

Fine-needle aspiration (FNA). A tiny needle pulls cells from a swollen node. Many cases can be diagnosed from this sample alone.

Lymph node biopsy. If FNA isn’t conclusive, a small piece—or rarely, the whole node—is removed to confirm the diagnosis and gather more detail.

Lab work. Blood and urine tests look for organ changes or infections that might alter the treatment plan.

Imaging. Chest X-rays and abdominal ultrasound check for enlarged organs or nodes and help plan therapy.

Immunophenotyping (T vs. B). Flow cytometry or similar tests identify cell type, which guides medication choices.

Curious how anemia fits into the picture? Read: What Kind of Cancer Causes Anemia in Dogs?

Staging: understanding “how far” it has gone

Staging describes how widely lymphoma has spread (often noted as Stage I–V). Your vet may recommend additional node sampling, imaging, and occasionally bone marrow testing. Staging doesn’t just label the disease—it helps tailor treatment to your dog’s situation.

Talking about outlook (and keeping it real)

Prognosis depends on the subtype (T vs. B), where the cancer is located, how your dog feels today, and how the cancer responds to the first few weeks of treatment. Some forms are indolent (slow) and manageable for long periods; others move faster and need a prompt, well-organized plan. Your vet will give ranges, not guarantees, and adjust the plan as your dog responds.

Treatment options (what most families choose first)

Chemotherapy
Because lymphoma is usually a systemic disease, chemo is the mainstay. Modern veterinary protocols use different drugs over a set schedule (for example, CHOP-style plans). The goal is quality time, not harsh side effects. Most dogs handle treatment well with only mild, short-lived tummy upset or lower energy after some visits.

Radiation therapy
Helpful for localized areas (e.g., nasal lymphoma) or for shrinking painful masses. It’s often combined with chemo or used for specific comfort goals.

Surgery
Less common for lymphoma, but sometimes used for diagnosis or unique, localized forms.

Supportive care
Nausea meds, appetite support, antibiotics when needed (to prevent secondary infections), and pain control when appropriate. This care matters as much as the cancer drugs—it keeps your dog comfortable while treatment does its job.

For a simple overview of treatment categories across cancers, see: Dog Cancer Tumor: What You Need to Know.

Remission: what it is—and what it isn’t

• Complete remission: we can’t detect active disease with the tools we typically use.

• Partial remission: there’s clear improvement, but some cancer remains.

• Relapse: lymphoma returns after remission.

If relapse happens, your team will talk about re-induction protocols or comfort-focused care. The plan can flex as your dog’s needs change.

Side effects: what to expect and when to call

Most dogs experience mild effects—lower appetite, softer stools, or a quiet day or two after treatment. Serious issues like fever, persistent vomiting/diarrhea, or refusal to drink deserve a same-day call. Many side effects can be prevented or quickly managed if you speak up early.

Living well during treatment

Keep routines predictable. Offer short, frequent walks. Use comfy bedding and non-slip rugs. Track appetite, energy, bathroom habits, and any meds in a notes app (or a simple notebook). Bring that log to appointments—it helps your vet spot patterns and adjust sooner.

If your dog has cutaneous lymphoma, ask your vet about gentle skin care and how to tell the difference between treatment irritation and disease activity.

Related reads you might find helpful:

• Understanding Skin Cancer in Dogs
• Understanding Dog Cancer in the Mouth
• Dog Breeds Most Prone to Cancer
• Understanding Canine Abdominal Tumors: Focus on Splenic Cancer

Where Oncotect fits (and where it doesn’t)

The  Oncotect Cancer Screening Test Kit is a non-invasive urine screen that supports earlier conversations about cancer risk—especially for seniors or higher-risk breeds. It screens for signals associated with several common cancers (including canine lymphoma). It doesn’t diagnose lymphoma; abnormal or concerning results should lead to a focused veterinary work-up (exam, FNA/biopsy, imaging). Think of it as an extra early-warning light on your dashboard—not the mechanic.

A practical checklist for pet parents

• Feel the common lymph node spots once a month.

• If something feels swollen or firm, jot the size and call your vet.

• Keep a simple daily log during treatment (appetite, energy, stool, meds).

• Ask which side effects deserve a same-day call.

• Schedule rechecks—don’t skip them when your dog “seems fine.”

Image suggestions (for your page layout)

1. Checking lymph nodes — vet gently palpating under a dog’s jaw (alt: “Where enlarged lymph nodes are commonly found”).

2. Node map diagram — silhouette showing submandibular, prescapular, axillary, inguinal, and popliteal node locations (alt: “Common canine lymph node locations”).

3. FNA sampling — close-up of a fine needle aspiration with calm handling (alt: “Fine-needle aspiration helps diagnose lymphoma”).

4. At-home comfort — senior dog resting on soft bedding with meds organizer nearby (alt: “Small routines make treatment days easier”).

5. Gentle walk — family on a short, happy walk with their dog (alt: “Light exercise supports well-being during therapy”).

6. Oncotect kit — clean, well-lit shot of the test kit and labeled urine cup (alt: “Non-invasive screening supports early detection conversations”).

Key takeaways

• Canine lymphoma is common and manageable, especially when you act early.

• The most consistent clue is enlarged lymph nodes —get them checked rather than guessing.

• Diagnosis usually starts with fine-needle aspiration, then adds imaging and advanced tests as needed.

• Treatment focuses on quality of life: modern chemo protocols, targeted radiation when useful, and strong supportive care.

• Keep an eye on changes, stick to rechecks, and use tools like Oncotect to support early detection and timely decisions.
  
  

If your dog’s lymph nodes feel big or your gut says, “Something’s off,” trust that feeling. Call your vet, get the basics done, and build a plan that fits your dog and your family. You’ve got this.