Lymphoma in Dogs

Lymphoma is one of the most common types of cancer affecting dogs.

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Unfortunately, most people have been directly or indirectly affected by cancer, and like people, our dog companions can develop cancer too. Lymphoma (also called lymphosarcoma or LSA) is one of the most common types of cancer affecting our dogs. Learning more about lymphoma can help pet caregivers be able to quickly recognize symptoms and act efficiently in getting their dogs the help they need. A cancer diagnosis is never an easy thing to deal with, but by understanding your dog's condition, you can make informed decisions with their happiness and wellbeing in mind.

What Is Lymphoma?

Canine lymphoma is a broad term that describes any type of cancer that involves lymphocytes, a type of white blood cell. However, there are actually many different forms of canine lymphoma, which are generally classified by the area of the body primarily affected and the type of lymphocyte involved. 

Lymphocytes are an important part of the immune system. Lymphocytes can be found anywhere in the body, but a large number of these cells are found in the lymph nodes, spleen, and intestinal tract. Because lymphocytes are found throughout the body, lymphoma can develop almost anywhere. 

Types of Lymphoma

There are different forms of this type of cancer, and they can be named based on the areas or organs on which they have an impact. The most common of the canine lymphoma types, accounting for approximately 80% of lymphomas, is multicentric lymphoma. Multicentric means having more than one center and this lymphoma will commonly involve several lymph organs including multiple lymph nodes and perhaps the spleen, liver, and/or bone marrow as well. Other relatively common canine lymphomas include alimentary (gastrointestinal) lymphoma, mediastinal lymphoma involving lymph nodes and/or the thymus within the chest, and extranodal lymphoma of organs like the skin, eyes, kidneys or nervous system.

Symptoms of Lymphoma in Dogs

The type of symptoms that develop depend on the location and stage of lymphoma. 

The most common initial finding is the presence of one or more enlarged, firm, and non-painful lymph nodes. Many dogs with multicentric lymphoma appear to feel just fine, but others can develop nonspecific signs like lethargy and loss of appetite.

Lymph nodes exist at many points throughout your dog’s body. Although there are dozens of lymph nodes throughout the body, only a few are easily palpable during a physical examination. The peripheral lymph nodes veterinarians and pet caregivers may be able to feel include:

  • Submandibular – located beneath the back of the jaw
  • Prescapular – located in front of the shoulder region
  • Axillary – located in the armpits
  • Inguinal – located in the groin
  • Popliteal – located behind the knees

Other symptoms typically relate to the location of the cancer. For example, with alimentary lymphoma, your dog may experience loss of appetite, nausea, vomiting, and diarrhea while lymphomas within the chest cavity can lead to difficulty breathing.

Causes of Lymphoma in Dogs

According to the Purdue University College of Veterinary Medicine, “Unfortunately, the cause of lymphoma in dogs is not known. Although several possible causes such as viruses, bacteria, chemical exposure, and physical factors such as strong magnetic fields have been investigated, the cause of this cancer remains unclear.” Genetics may play a role in some cases.

Diagnosing Lymphoma in Dogs

To diagnose lymphoma, the initial step is often a complete physical exam and a fine needle biopsy of the enlarged lymph node(s) submitted to a veterinary laboratory for analysis. In the case of a skin lesion, a skin biopsy can be submitted. In addition, a complete blood count, chemistry profile and urinalysis should be performed to identify abnormalities. Radiography of the chest and abdomen, plus abdominal ultrasound and/or a bone marrow biopsy may also be recommended to help determine the stage of the disease.

Lymphoma stages are based on what organs are affected and how many are involved, as well as sub-stages based on how the pet feels and how they are affected systemically.

The purpose of the staging tests is to determine how far the lymphoma has spread throughout your dog’s body. In general, the more places the lymphoma has spread to, the poorer the dog’s prognosis. However, dogs with very advanced lymphoma can still be treated and experience cancer remission or a meaningful improvement in their quality of life. Staging tests also help your veterinarian assess whether your dog has any other conditions that may affect treatment decisions or overall prognosis.

The stages are:

  • Stage I: Single lymph node involved
  • Stage II: Multiple lymph nodes in the same region involved
  • Stage III: Multiple lymph nodes in multiple regions involved
  • Stage IV: Liver and/or spleen involved (may or may not have lymph node involvement)
  • Stage V: Bone marrow or blood involvement and/or other organ besides liver, spleen and lymph nodes involved  

Treatment of Lymphoma in Dogs

There is currently no known cure for canine lymphoma, but it is one of the most treatable types of cancer in dogs. The most effective therapy for most types of canine lymphoma is chemotherapy. There is a wide variety of chemotherapy protocols and drugs that are currently being used to treat lymphoma. The treatment usually consists of a combination of oral and injectable drugs given on a weekly basis. Some commonly used drugs include cyclophosphamide, vincristine, doxorubicin, and prednisone. The exact treatment protocol will vary depending on the veterinarian and the specifics of the case. 

Fortunately, most dogs only experience mild side effects from chemotherapy and enjoy an excellent quality of life during treatment. Since lymphoma is generally not a curable disease, the goal of lymphoma treatment is to induce a lengthy remission, during which time all symptoms of the cancer have temporarily disappeared.

Radiation therapy or surgery can occasionally be an option for localized lymphosarcoma, but is usually combined with chemotherapy. 

Life Expectancy of Dogs with Lymphoma

You are most likely wondering, after a dog gets diagnosed, how this affects their life expectancy. Unfortunately, the answer is not always clear, and the prognosis depends on multiple factors including how the dog feels, what stage the cancer is, what stage it was when diagnosed, and treatments used. The prognosis with chemotherapy is relatively good, with most dogs experiencing either a partial or complete remission and a life expectancy of around one year, on average.