Lymphoma in Dogs

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

dog happy and running in grass

Brighton Dog Photography / Getty Images

Unfortunately, most people have been affected by cancer to some degree, and like people, our dog companions can develop cancer too. Lymphoma 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 dog 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 affects lymphocytes, a type of white blood cell. However, there are actually many different canine lymphoma types, with the primary types generally classified by the area the body primarily affected. 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 tonsils. Because lymphocytes are found throughout the body, lymphoma can develop in multiple places in the body. 

Types of Lymphoma

There are different forms of this type of cancer, and they are named based on the areas or organs on which they have an impact. The most common of the canine lymphoma types, accounting for 80% of lymphomas, is multi centric lymphoma. Multi centric means having more than one center and this lymphoma will commonly involve multiple lymph nodes and may also affect the spleen, liver, and/or bone marrow. Lymphoma also commonly originates in organs of the immune system such as the spleen and bone marrow. Other canine lymphomas include skin, stomach, intestines, and organs of the chest such as the thymus gland. 

Symptoms of Lymphoma in Dogs

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

The most common initial symptom is enlarged, firm, and non-painful lymph nodes. Lymph nodes are a very important part of the immune system and create the cells that help fight infection in the body and produce protection against diseases. 

Signs of Lymphoma in Dogs

  • Enlarged lymph nodes
  • Increased urination and drinking
  • Vomiting
  • Diarrhea/ Black tarry stool
  • Coughing 
  • Inappetence and nausea
  • Mild to severe weight loss
  • Irritability/reclusive behavior 
  • Swelling of the face or legs 
  • Shortness of breathing/Labored breathing
  • Weakness difficulty rising/ moving 
  • Lethargy

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 palpable during a physical examination. The lymph nodes veterinarians and pet caregivers may be able to feel are called peripheral lymph nodes and include:

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

Your dog may experience weight loss, loss of appetite, nausea, vomiting, diarrhea, and lethargy with gastrointestinal and stomach lymphoma. Skin lymphoma generally presents as what appears to be a skin infection that does not heal. Lymphomas within the chest cavity can cause fluid accumulation around the lungs leading 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”.

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 are also recommended to help determine the stage of the disease.

The 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. Staging tests also help your veterinarian assess whether your dog has any other conditions that may affect treatment decisions or overall prognosis.

The World Health Organization developed the staging system for dogs with lymphoma and 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. Fortunately, dogs tolerate the side effects of chemotherapy better than humans with milder manageable side effects. Since lymphoma is generally not a curable disease, the goal of lymphoma treatment is to induce a complete remission, by killing most of the cancer cells. The term “remission” means that all symptoms of the cancer have temporarily disappeared.

Surgery with radiation therapy can occasionally be an option if a single, local tumor exists, but is usually combined with chemotherapy. 

Although chemotherapy does not cure dogs with lymphoma, in most cases it does extend the length and quality of life. With treatment, in dogs that feel well, about 80 to 90 percent of dogs with lymphoma attain a complete remission with an average survival of 12 to 14 months. 

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 many organs the cancer cells have spread to, what stage the cancer is, what stage in which it was diagnosed, and treatments used. The prognosis with chemotherapy is good, with as high as 90 percent of dogs experiencing either a partial or complete remission. Keep in mind that a successful treatment can add up to a year of survival time, on average, to up to 50 percent of dogs.