Lymphoma in Dogs
Lymphoma is a cancer of the lymphoid cells and typically affects middle age to older dogs. It can develop primarily in lymph nodes or other organs in the body. There are two main types of lymphoma, B cell lymphoma and T cell lymphoma. In dogs, this type of cancer most commonly originates in the lymph nodes, but it can originate from the spleen, bone marrow, skin, or other organs. This can be a very aggressive cancer depending on the type and stage at the time of diagnosis. Continue reading to learn more about symptoms, tests, and treatment options for canine lymphoma.
What symptoms would I see if my dog has lymphoma?
Since lymphoma can arise from various organs, symptoms are not always the same. Often, you will notice weight loss, lethargy, GI upset such as vomiting or diarrhea, increased water intake and urination, and possibly fever (normal temperature for a dog is around 102F).
If cancer reaches the chest/thorax, it can cause labored breathing and exercise intolerance. Lymphoma can also primarily attack the skin and lead to hair loss, loss of pigmentation (normal coloration), nodules or firm plaques on the skin, skin ulcerations, and possibly redness to the skin.
Dogs most commonly develop lymphoma in the lymph nodes, so if you notice any lumps or bumps in the region of the lymph nodes, be sure to schedule an appointment with your vet right away for further testing. One or two enlarged lymph nodes can indicate a local infection that the body is trying to handle. Multiple enlarged lymph nodes are more concerning as it means a larger part of the body is being affected by something serious, such as cancer or tick-borne disease. Be sure to read our article on lymph node location in dogs so you know where to look on your pup!
What tests are needed if my vet suspects lymphoma?
Since lymphoma can arise from various organs, your dog may need multiple tests to help get a diagnosis. Initially, a good physical exam is needed to feel the external lymph nodes, deep palpation into the abdomen area to feel for internal lymph nodes or organ enlargement, and paying attention for any signs of other infections that may be causing similar symptoms in your dog.
Baseline lab work, including blood work (a CBC and chemistry panel) and urinalysis, are often the next steps. Lymphoma can cause severe changes in platelets, red and white blood cell levels. Lymphoma can also cause the calcium level to rise, protein levels in the body to rise, and can increase organ-specific enzymes if the cancer is present in them. The urine test will give additional information on kidney health and screen for urinary tract infections that need to be treated before starting chemotherapy treatment.
Cytology by fine-needle aspiration, directing a needle into an enlarged lymph node or skin lesions to obtain cells for evaluation, is another possible test. If your vet can feel an enlarged spleen or liver, they can even obtain cytology samples of these organs with ultrasound guidance. In dogs with lymphoma, there are often a large number of large lymphoblast cells present.
Flow cytometry is another test your vet may recommend. This test is run at specific diagnostic laboratories and can be run on blood, fine needle aspiration samples, or biopsy samples. This test can even tell what type, B or T cell, lymphoma is present and other information that can help determine the best treatment plan for your pup.
Immunohistochemistry is another type of test that gives similar information as flow cytometry. A biopsy sample is needed for this test. A biopsy is a larger tissue sample compared to fine-needle aspiration where just a cluster of cells is collected.
Lymphoma PCR test or PARR is another possible diagnostic tool. This test can be run on blood, tissue, or cytology samples. PARR helps try to figure out if the cause of your dogs’ illness is from an infection or cancer. However, it should not be used alone to diagnose cancer.
My dog has been diagnosed with lymphoma. What do we do now?
Now that your vet has run the necessary tests and confirmed your dog has lymphoma, it’s time to consider additional testing to stage the cancer or assess how far it’s progressed. This isn’t always necessary since treatment is typically systemic chemotherapy, so be sure to discuss these options with your vet.
Staging does help give an idea of the overall prognosis and gives an idea of average survival times with and without treatment. Tests include radiographs (x-rays) of the chest, ultrasound of the abdomen, echocardiogram (ultrasound) of the heart, bone marrow evaluation, and genetic testing for the MDR-1 Gene which can determine if certain chemotherapeutics are safe for your dog.
What treatment options are available for dogs with lymphoma?
Dogs with lymphoma that do not receive any treatment have average survival times of 2 months, so it’s important to start treatment as soon as possible. Dogs that do not have a good response to the initial treatment have a poor prognosis compared to dogs that do have a positive response to the initial treatment plan. However, even the dogs with a good response often relapse within a few months and need additional treatments to prolong their survival time and give a good quality of life.
Systemic chemotherapy is the main treatment for dogs diagnosed with lymphoma. The main chemotherapeutic treatment is a multi-drug protocol referred to as CHOP-Based Chemotherapy. This treatment involves 3 to 5 drugs, vincristine, cyclophosphamide, doxorubicin, prednisone, and sometimes L-asparaginase. This protocol typically involves weekly doses of chemotherapy for 4 to 6 months.
If your dog has an underlying heart condition or any heart abnormalities noted on an echocardiogram, they may not be a good candidate for doxorubicin treatment and need to do a modified chemotherapy protocol without that drug. Unfortunately, the effectiveness of treatment is not as good without doxorubicin.
Finally, if the cost of the CHOP treatment is too much, you can discuss a single chemotherapeutic treatment, often just with doxorubicin. This treatment is given every 3 weeks for 5 to 6 doses. It isn’t as effective as the CHOP protocols, but it does help slow the progression.
B cell lymphoma patients tend to respond better to chemotherapy treatment compared to T cell lymphoma patients.
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