Catherine Barnette, DVM, of VCA Hospitals, an operator of over 1,000 animal hospitals in the US and Canada, defined lymphoma as a cancer of the lymph nodes and lymphatic system. Lymphoma may be localized to a particular region or may spread throughout your pet’s body.
The lymphatic system has lymph nodes, specialized lymphatic organs like the spleen and tonsils, and the lymphatic vessels. These components are responsible for the movement of fluids and other substances in the body and respond to toxins or infections thanks to their immune functions.
Lymphoma is a common cancer among humans and dogs, which can be terrifying for owners, said Anna Burge of the American Kennel Club, a trusted expert in breed, health, and training information for dogs. Helping you understand canine lymphoma can help you make more informed decisions about your dog’s health and condition.
A Survey of Morphology and Immunophenotypes of Canine Lymphomas (2011)
Katia C. Kimura and colleagues of electronic journal portal Brazilian Journal of Veterinary Pathology collected wax-embedded tissue samples from 65 canine lymphomas from 1995 to 2009 from the Service of Animal Pathology of FMVZ-USP, Sao Paulo, Brazil. Breed distribution showed the prevalence of Mixed breed (43%), Boxer (14%), German Shepherd (11%), and Brazilian Terrier (3%).
The prevalence of canine lymphoma was higher between five to nine years (45% of total cases), along with ages between 10 to 13 years (34%), below four years (17%), and up to 14 years (5%). Regarding anatomical distribution, the authors found that 37% of cases were multicentric lymphadenopathy, 23% were extranodal, 20% were cutaneous, 18% were in the alimentary tract, and 2% were mediastinal. Among 65 canine lymphomas, 85% had T-cell origin while 15% had B-cell origin. However, none had B-cell and T-cell origin.
The T-cell lymphomas were further categorized as the following: pleomorphic small cell (34%), cutaneous T-cell, high grade (20%), lymphoblastic (18%), aggressive large granular cell (7%), and pleomorphic mixed (5%). T-cell origin (51%) had a high mitotic index while 34% had a low mitotic index. On the other hand, 9% of B-cell origin had a high mitotic index while 6% had a low mitotic index.
The authors obtained the following values from the histological subtypes of cutaneous T-cell lymphoma: cerebriform small (mycosis fungoides) (54%), cerebriform large cell in transformation immunoblastic (15%), blastic (15%0, monocytoid (8%), cerebriform small cell (8%).
Other subtypes included cutaneous T-cell, low grade (4%), pleomorphic large cell (4%), plasmacytoid (4%), immunoblastic (2%), and prolymphocytic (2%). The B-cell lymphomas were categorized into: centroblastic polymorphic (30%), Burkitt (20%), lymphoplasmaytic (20%), anaplastic/mediastinal (10%), small lymphocytic (10%), and prolymphocytic (10%).
Mixed breed was the most affected while Boxers were predominated by T-cell lymphoma, Kimura and colleagues concluded. However, further research is required to tackle the possible factors that caused the development of lymphoma among canines.
How Common Is Lymphoma Among Dogs?
Lymphoma commonly occurs in middle-aged and older dogs and some breeds like Boxer dogs, Golden Retrievers, Bulldogs, and more are pre-disposed to this cancer. The most common type of canine lymphoma is multicentric (systemic) lymphoma, representing about 80% to 85% of cases of canine lymphoma. Lymph nodes in your dog’s body are affected when it has systemic lymphoma. Alimentary lymphoma affects your dog’s gastrointestinal tract and is the second most common type of lymphoma.
Mediastinal lymphoma is a rare form of lymphoma affecting the lymphoid organs in the chest like the thymus or lymph nodes. Extranodal lymphoma affects a specific organ outside of your pet’s lymphatic system. It is a rare form of lymphoma but it may occur in the nervous system, kidney, lung, skin, or eyes.
What Are the Symptoms of Lymphoma?
In systemic lymphoma, one sign is swelling of the lymph nodes. Lymph nodes located in the chest, neck, armpits, groin, and behind the knees are usually the most visible. Most dogs do exhibit clinical signs of illness during diagnosis. However, they may often experience weight loss and lethargy if lymphoma is untreated.
In other less common types of lymphoma, symptoms may occur on the organ affected by the cancer. For example, alimentary lymphoma causes gastrointestinal lesions, causing diarrhea, vomiting, and weight loss. Mediastinal lymphoma causes lesions in the chest, occupying the chest cavity and leading to shortness of breath and coughing. Likewise, the symptoms of extranodal lymphoma may differ as it depends on the organ affected by this form of lymphoma.
How Is Lymphoma Diagnosed?
Your veterinarian will perform a diagnosis by obtaining a sample of your pet’s affected organ if cancer is suspected. The most common diagnostic tool is fine-needle aspiration, which involves getting a sample of your dog’s lymph nodes or organs to be examined through cytology exam or by a histopathologic evaluation.
Some veterinarians recommend “staging tests” after a lymphoma diagnosis to see how far has the cancer progressed throughout your canine’s body. “Staging tests” allow veterinarians to understand your pet’s overall condition and the cancer. This may include urinalysis, x-rays, blood tests, abdominal sonograms, and bone marrow aspiration.
How Is Lymphoma Treated?
It is treated with chemotherapy, but there are a variety of procedures performed to address lymphoma. However, most treatment plans involve a variety of injections given every week. Dogs tolerate chemotherapy better than humans, meaning they rarely lose their hair or fall ill.
However, the most common side effects of chemotherapy are diarrhea, vomiting, and decreased appetite—though these effects are not present in all dogs. Surgery and/or radiation may be used to treat certain types of low-grade localized lymphoma. Notably, most cases cannot be treated with surgery or radiation. Prednisone can be given for palliative care if chemotherapy is not a viable option for you due to financial constraints or any other factor. Prednisone does not treat lymphoma, but it can temporarily reduce the clinical signs of the cancer.
What Is the Prognosis for Canine Lymphoma?
The prognosis varies depending on the stage of your pet’s lymphoma at the time of treatment, as well as the choice of treatment. Lymphoma can be put into remission if your dog undergoes chemotherapy. It is never “cured” as remission means that all symptoms of lymphoma are not present in your dog. Remission with chemotherapy is around eight to nine months and it has an estimated average survival time of one year with chemotherapy.
Canine lymphoma may cause distress among owners. Owners should be proactive about knowing their veterinarian’s available treatment options and the type of cancer itself. If they suspect their dog has lymphoma, owners should call their veterinarian for early intervention.