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Lymphoma in dogs: blood work, calcium and diagnosis

Lymphoma is one of the most common cancers in dogs. Most dogs are brought in for firm, painless swellings under the jaw, in front of the shoulders or behind the knees. Blood tests rarely make the diagnosis on their own, but they give important clues and help plan the next steps.

Written by the AI DiagAnimals editorial teamReviewed by the AI DiagAnimals TeamUpdated Our editorial policy

The essentials

Lymphoma usually shows as several enlarged lymph nodes. The diagnosis is made on a sample of a node: a fine-needle aspirate first, sometimes a biopsy, then the cell type (B or T cell). The blood count can show mild anemia or low lymphocytes. A high calcium points towards T-cell lymphoma and is found in about 1 dog in 9 with the common multicentric form.

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What lymphoma looks like

Lymphoma is a cancer of lymphocytes, a type of white blood cell. It makes up about 6% of cancers in dogs and 90% of blood-cell cancers [1]. Most dogs have generalized enlarged lymph nodes (the multicentric form), and most lymphomas are intermediate- to high-grade and of B-cell type [2].

Other forms exist: in the chest (mediastinal lymphoma, almost always T-cell, with fluid around the lungs and increased thirst), in the gut, the skin, or slow-growing forms found by chance [1, 3].

What the blood count shows

  • Anemia in about 37% of dogs with large B-cell lymphoma, usually mild to moderate and non-regenerative [4].
  • Low lymphocytes in 35%, high neutrophils in 26% and high monocytes in 29% in the same study [4].
  • Low platelets were more frequent than high platelets [4].
  • High lymphocytes are uncommon in most forms, but frequent in the slow-growing T-zone lymphoma (48–64% of cases) [1].

A normal blood count does not rule out lymphoma. See the CBC for dogs.

High calcium: a key clue

Some lymphomas release a hormone-like protein (PTHrP) that raises blood calcium. T-cell lymphoma is the most common tumour to cause high calcium in dogs, followed by anal sac gland tumours [5]. In a study of 411 dogs with multicentric lymphoma, 11.4% had a high calcium [6].

An annotated line from a lab report · Illustrative example
AbbreviationResultUnitLaboratory intervalFlag
Ca Calcium (total)14.2mg/dL9.1–11.7H
  1. Abbreviation Ca or CALC: total calcium. Ionized calcium (iCa) confirms a true rise.
  2. Result 14.2 mg/dL in this illustrative line: clearly high.
  3. Unit mg/dL in the US; mmol/L elsewhere (mg/dL ÷ 4.008).
  4. Laboratory interval An illustrative dog interval; each laboratory sets its own.
  5. Flag H: above the interval. With enlarged lymph nodes, vets look for lymphoma first. See high calcium in dogs and cats.

Unit converter

Equivalent values

  • Calcium, mmol/L–
  • Calcium, mg/L–

Conversion only changes the unit. Compare the result with the interval printed by the laboratory that measured it.

How lymphoma is confirmed

  • Fine-needle aspirate of a lymph node: a highly sensitive and specific first test for the common large-cell forms [1].
  • Biopsy of a whole lymph node: the gold standard, needed for small-cell and nodular forms where a needle sample is not enough [1].
  • B or T cell type (immunophenotype): considered essential, because it changes the outlook and the treatment plan. It is obtained by immunohistochemistry, flow cytometry or PARR [1].
  • PARR looks for a single clone of lymphocytes. On aspirates, one study found 100% sensitivity and specificity; on other samples results can be equivocal and must be read with the rest [7].

Outlook

With doxorubicin-based chemotherapy, median remission is 7–10 months and median survival 10–14 months [2]. Your vet will usually stage the disease with blood tests, imaging and sometimes a bone marrow sample before discussing options.

Related articles

White blood cell count in dogs

Lymphocytes, neutrophils and monocytes.

Read the article

For cats, see lymphoma in cats. En français : lymphome du chien.

Questions to ask your veterinarian

  1. Is the calcium high, and should we measure ionized calcium?
  2. Is a needle sample enough, or is a biopsy needed?
  3. Is it B-cell or T-cell lymphoma?
  4. What does staging involve, and what do the blood count and chemistry show?
  5. What are the options and the expected outlook for my dog?
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Frequently asked questions

What is the life expectancy of a dog with lymphoma?

With doxorubicin-based chemotherapy, median survival is about 10–14 months. It depends on the type (B or T cell), the stage and the dog’s general condition [2].

Can blood tests detect lymphoma in dogs?

Not on their own. They can give clues, such as high calcium or abnormal lymphocytes, but the diagnosis is made on a lymph node sample [1, 5].

Are dogs in pain with lymphoma?

Enlarged lymph nodes are usually not painful. Discomfort depends on the organs involved; ask your vet about pain relief if your dog seems unwell.

Which type of lymphoma causes high calcium?

Mainly T-cell lymphoma, including the mediastinal form in the chest [3, 5].

What is PARR?

A test that checks whether the lymphocytes in a sample come from a single clone, as in cancer, or from many clones, as in a reaction to infection or inflammation [7].

Sources

  1. Seelig DM et al. The Comparative Diagnostic Features of Canine and Human Lymphoma. Vet Sci. 2016;3(2):11. doi.org/10.3390/vetsci3020011
  2. Zandvliet M. Canine lymphoma: a review. Vet Q. 2016;36(2):76-104. doi.org/10.1080/01652176.2016.1152633
  3. Moore EL et al. Patient characteristics, prognostic factors and outcome of dogs with high-grade primary mediastinal lymphoma. Vet Comp Oncol. 2018;16(1):E45-E51. doi.org/10.1111/vco.12331
  4. Gavazza A et al. Hematological ratios and indices in canine large B-cell lymphoma. Open Vet J. 2024;14(4):980-989. doi.org/10.5455/OVJ.2024.v14.i4.5
  5. eClinPath, Cornell University College of Veterinary Medicine. Calcium. eclinpath.com/chemistry/minerals/calcium
  6. Ernst T et al. Multicentric lymphoma in 411 dogs – an epidemiological study (in German). Tierarztl Prax Ausg K Kleintiere Heimtiere. 2016;44(4):245-251. doi.org/10.15654/TPK-150338
  7. Ehrhart EJ et al. Polymerase chain reaction for antigen receptor rearrangement: benchmarking performance of a lymphoid clonality assay in diverse canine sample types. J Vet Intern Med. 2019;33(3):1392-1402. doi.org/10.1111/jvim.15485

Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.

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