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Diagnostics2026-06-18 · 12 min read

Canine Lymphoma: Diagnosis, WHO Staging, CHOP, and Prognosis (B-Cell vs T-Cell)

Canine lymphoma workup — FNA cytology vs biopsy, flow cytometry and PARR, WHO staging and immunophenotype, CHOP vs doxorubicin vs Tanovea vs oral Laverdia, and what remission and survival look like.

Ran Chen
Ran Chen
Founder, VetMedGuide. Life-sciences operator and 10× global market-access lead.
Published

Lymphoma is one of the most common cancers in dogs, accounting for an estimated 80% or more of hematopoietic tumors and roughly a quarter of all canine cancer diagnoses. Cancer overall affects about half of dogs over 10 years of age, and lymphoma is a large share of that burden. The disease also has an unusually clear treatment story for a cancer: it responds well to chemotherapy, most dogs go into remission, and the central questions for an owner are about time and quality of life, not cure, because lymphoma in dogs is treatable but almost never curable.

This article is the diagnostic and staging workup for the most common form, multicentric (generalized) lymphoma, and the treatment landscape that follows it. It covers how the diagnosis is confirmed, what staging and immunophenotyping change about the prognosis, how a veterinarian chooses between multi-drug CHOP chemotherapy and simpler options such as single-agent doxorubicin or the FDA-approved drugs Tanovea (rabacfosadine) and oral Laverdia (verdinexor), and what remission and survival times to realistically expect. For when to involve an oncologist, see oncology referral timing; the 2026 AAHA Oncology Guidelines for Dogs and Cats give primary-care teams the framework for much of what follows.

Quick answer

Canine lymphoma is a systemic cancer of lymphocytes that most often appears as painless, generalized enlargement of the lymph nodes (under the jaw, in front of the shoulders, behind the knees, and internally in the liver, spleen, and bone marrow). It is diagnosed with a fine-needle aspirate and cytology of an enlarged node, confirmed and subtyped with flow cytometry or biopsy to determine whether it is B-cell or T-cell, and then staged with bloodwork, urinalysis, thoracic radiographs, and abdominal ultrasound (and sometimes bone marrow sampling). Treatment is systemic chemotherapy, and the multi-drug CHOP protocol (cyclophosphamide, doxorubicin, vincristine, and prednisone) is the standard of care — it sends over 80% of B-cell lymphomas into complete remission with a median survival of about 12 to 14 months. Left untreated, most dogs live only 4 to 6 weeks. The single most important prognostic factor a staging workup delivers is the immunophenotype: B-cell lymphoma responds substantially better and lasts longer than T-cell lymphoma, which is the result owners most need to understand before committing to treatment.

What lymphoma looks like, and why the form matters

The vast majority of canine lymphoma is multicentric — involving multiple lymph node regions at once — and that is the form this article addresses. Dogs present with firm but non-painful swellings at the peripheral lymph nodes that have often grown over days to a few weeks; the easiest nodes for an owner to feel are under the jaw (submandibular), in front of the shoulders (prescapular), and behind the knees (popliteal). With more advanced disease they may also show lethargy, weight loss, reduced appetite, and general decline. A subset of dogs — particularly some T-cell variants — develop paraneoplastic hypercalcemia (abnormally high blood calcium from a substance the tumor secretes), which shows up as markedly increased thirst and urination and is itself a finding that warrants a cancer workup. Less common anatomic forms — gastrointestinal, mediastinal, cutaneous, and central nervous system — behave differently, carry different prognoses, and need their own workup. Multicentric lymphoma is also typically high-grade (intermediate- to large-cell), which matters because high-grade disease is what responds so well to CHOP.

Typical signalment: middle-aged to older dogs are most often affected, and certain breeds — Golden Retrievers, Boxers, Bulldogs, and others — are overrepresented, though any breed can develop the disease.

Confirming the diagnosis: aspirate, biopsy, and clonality

Fine-needle aspiration (FNA) with cytology is the preferred first diagnostic step. It is rapid, inexpensive, and minimally invasive, and for the common high-grade lymphoma it is usually enough to make the diagnosis: a cytologist sees a uniform population of large, immature lymphocytes effacing the node. Cytology can be inadequate for low-grade lymphomas or for sorting out reactive (inflammatory) nodes from truly neoplastic ones, and in those cases a surgical biopsy with histopathology is needed. Histopathology remains the gold standard for assigning grade and architectural subtype, and it enables immunohistochemistry to stain the cells as B-cell (CD79a) or T-cell (CD3).

Two molecular tools have moved into routine use alongside cytology. Flow cytometry — run on a needle-rinsed sample or on blood — identifies the cells by size, complexity, and surface markers (the CD markers), giving both a diagnosis and an immunophenotype from a single non-surgical sample. The PCR for antigen receptor rearrangement (PARR) assay demonstrates clonality: it shows that the lymphocytes all descend from a single original malignant cell, which is strong evidence of cancer rather than inflammation. PARR can be run on aspirates, stained slides, or biopsy tissue and is also useful later for detecting early relapse, but it cannot be run on blood unless malignant cells are circulating (typically Stage V). In practice, FNA cytology plus flow cytometry now answers most of what an oncologist needs to start treatment, with biopsy reserved for ambiguous or low-grade cases.

Staging: how far has it spread, and the substage that predicts outcome

Once lymphoma is confirmed, staging documents how far it has spread and provides the baseline for later monitoring. The WHO clinical staging system (also used in other domestic animals) runs from Stage I (a single node involved) through Stage II (regional nodes), Stage III (generalized peripheral nodes), Stage IV (liver and/or spleen), and Stage V (blood, bone marrow, or other organs). The practical reality is that more than 80% of dogs are diagnosed at Stage III or higher, because multicentric lymphoma is systemic by the time it is noticed. A second, separate descriptor — the substage — often predicts outcome more sharply than the stage itself: substage a means the dog feels well and has no systemic signs, while substage b means there are systemic signs such as weight loss, lethargy, or poor appetite. Substage b dogs do worse.

A full staging workup typically includes a complete blood count with smear review, serum chemistry, urinalysis, thoracic radiographs, and abdominal ultrasound, with bone marrow aspiration added when Stage V is suspected or to complete the picture. Staging is not strictly required to begin treatment — a diagnosis, recent bloodwork, and a urinalysis are enough to start — but it sets expectations, reveals complications, and informs prognosis. The most prognostically important result of the whole workup, however, is usually not the stage but the immunophenotype.

The single most important result: B-cell vs T-cell

Approximately 80% of canine lymphomas are B-cell and roughly 18% are T-cell (a small fraction are null-cell). This split matters because B-cell lymphoma responds far better to CHOP chemotherapy, achieves higher and longer remission rates, and carries a substantially longer median survival than T-cell lymphoma. T-cell phenotype, higher stage, substage b signs, and certain anatomic locations all point toward a more guarded prognosis. Knowing the phenotype before treatment lets a veterinarian give an honest prognosis and, in some cases, adjust the protocol — which is why immunophenotyping (by flow cytometry, PARR, or biopsy immunohistochemistry) is now considered part of a thorough workup rather than an optional add-on.

Treatment: CHOP, single-agent options, and the FDA-approved drugs

CHOP-based chemotherapy is the standard of care for multicentric lymphoma and the protocol against which everything else is measured. The acronym is built from its drugs: Cyclophosphamide, Hydroxydaunorubicin (doxorubicin), Oncovin (vincristine), and Prednisone. The widely used University of Wisconsin–Madison protocols run roughly 19 or 25 weeks across four cycles. With CHOP, complete remission is achieved in over 80% of B-cell lymphomas, with median remission durations commonly in the 8 to 11 month range and a median survival of about 12 to 14 months; roughly a quarter of treated dogs become long-term survivors beyond two years. Recent evidence has simplified how CHOP is delivered — adding L-asparaginase at the start does not clearly extend survival (so it is often saved for rescue), and a continuous maintenance phase is no longer favored over a discontinuous protocol, which seems to leave the tumor more responsive at relapse.

The catch with lymphoma is that remission is not cure, and roughly 95% of treated dogs eventually relapse. When that happens, the length of the first remission predicts the next: dogs that stayed in remission longer tend to respond better to re-treatment, while dogs that relapse early or during the protocol have a harder road. Rescue (salvage) options include restarting CHOP if enough time has passed, and single agents such as L-asparaginase, lomustine (CCNU), the LAP combination, and rabacfosadine. Doxorubicin has a cumulative heart-dose limit and is typically swapped for mitoxantrone after about six doses. Cost is a real part of the decision: a full CHOP protocol commonly runs several thousand dollars over its 19–25 weeks (in the range of $500–$700 per treatment visit at many referral hospitals), while single-agent doxorubicin or the newer oral/injectable options reduce visit frequency at the cost of somewhat shorter remission — prednisone alone is cheap but buys only weeks to a couple of months and can make later chemotherapy less effective.

For owners who cannot manage frequent visits or a long multi-drug protocol, single-agent doxorubicin (the single most effective CHOP drug, given roughly every three weeks for five treatments) is a reasonable alternative that still frequently produces remission, though shorter than full CHOP. Two newer options occupy specific niches:

  • Tanovea-CA1 (rabacfosadine), an injectable drug given about every three weeks, was the first treatment to reach full FDA approval for canine lymphoma (conditional approval in 2016, full approval in 2021) and remains the fully approved injectable option — Laverdia is the fully approved oral option. In a randomized, placebo-controlled multicenter trial in 158 dogs, the best overall response rate was about 73%, with median progression-free survival around 151–172 days in responders; it is most often used after CHOP or as part of a rescue plan rather than as first-line induction. It carries a labeled risk of pulmonary fibrosis and is contraindicated in West Highland White Terriers and other dogs predisposed to the condition.
  • Laverdia-CA1 (verdinexor), an oral at-home tablet, received full FDA approval in January 2026 (after conditional approval since 2021). As a single agent it does not match CHOP response rates — its pivotal field study showed a median time to progression of about 37 days versus 23 days for placebo — but it fills a distinct niche for owners who cannot pursue injectable chemotherapy or whose dogs have relapsed. Its mechanism (blocking exportin 1 and trapping tumor-suppressor proteins in the nucleus) is different from CHOP, so it can work when conventional drugs no longer do; chemo-handling safety at home is an important part of counseling (covered in the Laverdia article).

For owners who decline chemotherapy entirely, prednisone alone can temporarily shrink nodes and improve how the dog feels, but the benefit is short (weeks to a couple of months) and it can make later chemotherapy less effective. The overriding principle of veterinary oncology, emphasized in the 2026 AAHA Oncology Guidelines, is that the goal of systemic therapy is quality of life while controlling disease — most chemotherapy protocols are well tolerated, and adverse events are usually manageable when they are anticipated and monitored.

What monitoring and prognosis look like

  • During treatment: a CBC before each chemotherapy dose (especially the morning of vincristine, cyclophosphamide, and doxorubicine) to confirm adequate neutrophils, and node measurement at each visit to confirm and track remission.
  • After induction: periodic rechecks to detect relapse early, since most dogs will relapse; relapse is usually first noticed as re-enlarging nodes and confirmed by aspirate.
  • Prognosis to set expectations: untreated median survival is only 4–6 weeks; with CHOP, median survival is roughly 12–14 months for B-cell disease, with about 25% of dogs exceeding two years; T-cell phenotype, substage b, and higher stage shorten those numbers.
  • When to refer: complex staging, advanced imaging, the desire for a full CHOP protocol or the newer FDA-approved drugs, and any decision balancing curative versus palliative intent are referral triggers — early collaboration with an oncologist tends to improve both outcomes and client confidence.

Lymphoma is one of the cancers where primary-care teams can do a great deal — establish the diagnosis, stage the patient, frame an honest prognosis around the immunophenotype, and either initiate a simpler protocol or coordinate referral for CHOP. The conversation that matters most is the one about expectations: treatment buys good-quality time, usually measured in months to low-double-digit months for B-cell disease, almost never a cure, and the workup's job is to tell an owner exactly where their dog sits on that curve.

Sources

Topics
Oncology
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