Canine Lymphoma: Symptoms, Diagnoses, and Treatment

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What is Canine Lymphoma in Dogs?

Canine lymphoma is a cancer for lymph nodes and of the lymphatic system which accounts of 15-20% of new cancer diagnoses in dogs. The lymphatic system is made up of lymph nodes and is a part of the immune system. The lymphatic system is made up of lymphatic veins that drain extra fluid from tissue, collect lymph (fluid), and filter blood. It functions more as a body’s storage container and filter.  Lymphocytes, which are white blood cells, make up the majority of lymph.  The lymph nodes house lymphocytes, which circulate in the blood and lymph. Like fevers, the lymphatic system aids the body in the battle against infections, making it one of the first signs of sickness.

While canine lymphoma can occur anywhere in the body, the most common occurrences are in organs that function as a part of the immune system. This includes bone marrow, spleen, and lymph nodes.

There are actually more than 30 different types of canine lymphomas but four are the most common types:

Multicentric Lymphoma
85% or more of lymphoma cases are multicentric making it the most common type of lymphoma. In multicentric lymphoma, the lymph nodes are impacted all across the body.

By far, this is the most typical kind of canine lymphoma. Eighty to five percent or more of canine lymphoma cases are multicentric. The lymph nodes across the body are impacted by multicentric lymphoma.

Alimentary Lymphoma
The second most common type of canine lymphoma is coming in at less than 10% of all lymphoma cases and affects the gastrointestinal tract.

Mediastinal Lymphoma
Mediastinal lymphoma is a rare form of lymphoma that affects the lymphoid organs in the chest.

Extranodal Lymphoma
Extrondal lymphoma is rare and targets specific organs outside of the lymphatic system such as the skin, eyes, lungs, kidneys, or nervous system.

What Causes Canine Lymphoma in Dogs?

Unfortunately, there isn’t much known about what causes lymphoma in dogs but it’s believed that advanced genetic studies will one day help identify any underlying genetic and chromosomal causes and predispositions. We do know that dogs live in the same environment as humans, and as a result, they are exposed to many of the same carcinogens, including dangerous compounds like phenoxyacetic acid herbicides and magnetic field exposure.

Who’s at Risk of Developing Canine Lymphoma?

While lymphoma is a fairly common type of cancer, it’s been noted that it’s most prevalent in middle-aged to senior dogs which certain breeds being more predisposed than others. Some breeds that are predisposed to canine lymphoma are Basset Hounds, Scottish Terriers, Saint Bernards, Golden Retrievers, Airedale Terriers, Bullmastiffs, Bulldogs and Boxers. Due to certain breeds being predisposed, this increases the belief that there may be a genetic component to canine lymphoma.

What are the Symptoms of Canine Lymphoma?

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There are numerous symtoms of canine lymphoma which can vary due to the stage, the type and how aggressive it is. 

Initial symptoms of multicentric lymphoma, which is the most common type include: 

  • Swelling of the lymph nodes
  • Loss of appetite
  • Lethargy
  • Weight loss
  • Swelling of the ace or legs
  • Increased thirst or urination

When it comes to the less common forms of lymphoma, the symptoms mostly depend on the affected organs. For example, vomiting, diarrhea, and weight loss are symptoms of gastrointestinal lesions brought on by gastrointestinal lymphoma. Lesions in the chest caused by mediastinal lymphoma enlarge the chest cavity and frequently cause coughing and shortness of breath.

Can Canine Lymphoma be Prevented?

Just like in people, there are some factors that may increase a dog’s risk for developing canine lymphoma. The first factor is environmental factors. Certain environmental factors increase the risk of cancer in humans. By combining data on radon, herbicide, and fungicide levels in the environment, researchers in Britain discovered a connection between fungicide exposure and canine lymphoma. This theory has also been tested in France and Brazil linking canine lymphoma to radioactive waste waste incinerators, and polluted sites. Keep in mind that these studies have not proven the connection but it’s recommended to keep your dog away from these kinds of environmental factors.

Just like in humans, hormones have an affect on increasing the risk of cancer in canines. A study was completed by the University of Missouri by veterinarians that observed the developlent of canine lymphoma in over one million dogs. Using a database of more than one million canines, veterinary researchers at the University of Missouri examined the impact of hormones on the emergence of canine lymphoma. Since spaying and neutering suppress the production of reproductive hormones, these researchers compared dogs that had had these procedures versus canines that had not. They discovered that female dogs are less likely to develop lymphoma than male dogs, and intact female canines are less likely to develop the disease than spayed females. Spaying, however, provides health advantages that may outweigh the risk of cancer.

There are many factors that AREN’T in your contnrol such as whether your dog came to you spayed, or you live in an urban environment that has numerous environmental factors that are linked to lymphoma that your dog is exposed to. But there are certain factors that you CAN control. The main thing you can control is keeping your dog at a healthy weight which in general leads to a longer, healthier life on average. If your dog is overweight, you can follow simple steps to get them on the right track.

How is Canine Lymphoma Diagnosed?

The first stage in diagnosing lymphoma is often a fine needle aspirate. If that doesn’t give results, the next step to diagnose lymphoma, as with other cancers, is a biopsy. Keep in mind that enlarged lymph nodes don’t always indicate lymphoma so the veterinarian will usually want to conduct further tests to find out why your dog has enlarged lymph nodes. Bloodwork is usually done to determine your dog’s overall health which includes a complete blood cell count  and serum biochemistry.

If these previous tests indicate lymphoma, additional testing is usually done. What’s usually done is called “staging tests”. This will help indicate how far along your dog’s lymphoma has progressed. The following tests are usually done during staging testing:

  • Blood tests
  • Urinalysis
  • Chest and abdomen x-rays
  • Abdominal ultrasonography
  • Bone marrow aspirate

What is the Treatment for Canine Lymphoma?

Photo Credit: Ethos Veterinary Health

As with human cancer, chemotherapy is the most recommended and effective form of treatment for canine lymphoma. Chemotherapy, luckily, is not as harmful to dogs as it is for humans. Dogs don’t experience hair loss or feeling significantly ill as often as humans. The more common side effects include vomiting, diarrhea, and decreased appetite but not all dogs experience it. For this treatment, injections are given weekly. For some low-grade localized lymphoma types, surgery and/or radiation therapy may be helpful, although these treatments are unsuccessful in the majority of instances. 

If palliative care is the route chosen, prednisone is often used. It won’t treat the cancer but it will assist in reduction of symptoms to give your dog comfort and give them some time.

What is the Prognosis for Canine Lymphoma?

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When it comes to the prognosis of canine lymphoma, there are multiple determining factors such as the type, severity, and progression. Dogs who receive no treatment whatsoever often have an expected survival rate of approximately 4-6 weeks. Keep in mind that this is just an average some dogs don’t make the 4-week mark and some make it past the 6-week mark.

Lymphoma can often be put into remission with the use of chemotherapy. Just like other cancers, it can’t be cured. But chemotherapy can result in the average remission being 8-9 months with an average one-year survival time. Your veterinarian will be able to provide a better estimate based on the factors mentioned above and how your dog is responding to treatment.

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