Canine lymphoma, similar to non-Hodgkin lymphoma in humans, accounts for about 7 to 14 percent of all canine cancers and is one of the five most common in dogs. There are more than 30 types described, which can differ significantly in their behavior.
What is it?
Lymphoma is made up of white blood cells called lymphocytes, which help the immune system fight off infection. As a result, most lymphomas are found in organs that are part of this system.
While lymphoma can affect almost any of these organs, it most commonly occurs in the lymph nodes under the jaw, in front of the shoulders, or behind the knee joint before spreading to another organ such as the spleen, liver, or bone marrow. Some lymphomas develop quickly and require aggressive treatment, while others are very slow moving and can be treated as a chronic disease. Like most canine cancers, lymphoma has no known cause.
The four most common types are multicenter (80 to 85 percent of lymphomas) and affect the lymph nodes. Food (7 percent of lymphomas) that affects the intestines; mediastinal, affecting the thymus and breast nodes; and extranodal, which affect a specific organ such as skin, eyes, kidneys, lungs or the central nervous system. (If the bone marrow is affected, the diagnosis is lymphocytic leukemia.)
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Signs and symptoms.
In the early stages of lymphoma, a dog owner may notice a lump under the dog’s jaw or neck without the dog showing any signs of illness. Some dogs may show just mild fatigue or decreased appetite, while others may have more severe symptoms such as weight loss, weakness, GI problems, excessive thirst, or difficulty breathing. Swollen, pain-free lymph nodes are a consistent sign.
Lymphomas (cutaneous lymphomas) that appear on the skin are sometimes first diagnosed as an infection or an allergy. They start out with red, scaly, itchy patches that eventually turn into red, damp, open sores. Gastrointestinal lymphoma with vomiting; dark, watery diarrhea; and weight loss. Lymphomas that occur in the chest can cause a dog to have difficulty breathing and / or develop a swollen face and front legs.
How is it diagnosed?
To diagnose lymphoma, the vet will biopsy the affected tissue and then do a series of tests to see how far it has developed. Blood and urine will be evaluated, chest and abdomen X-rayed, and an abdominal sonogram and bone marrow aspirate may be recommended. Abnormalities revealed by the sonogram are often examined with fine needle aspirate, a well-tolerated way to obtain a sample of the mass.
How is it treated?
Depending on the type, lymphoma is generally considered treatable and chemotherapy is the preferred method.
According to experts at Colorado State University’s Flint Animal Cancer Center, “Canine lymphoma is initially very sensitive to chemotherapy. Up to 95 percent of treated dogs go into remission when the most effective treatment protocols are used. “These protocols involve a combination of drugs given over weeks to months and are based on a similar protocol used for lymphomas that occur in humans.
A recent therapy, Tanovea-CA1, which was subject to FDA approval, shows great promise. It can be used alone or in combination with other drugs and includes five intravenous infusions of the drug at twenty-one day intervals. The drug is expensive, but it can result in a lower overall cost because the course of treatment tends to be shorter than other options.
Dogs being treated for lymphoma typically have a very good quality of life and often remain in remission for a year or more. About 20 percent of dogs survive more than two years with appropriate treatment.
Are Certain Races Predisposed?
Lymphomas can develop in any breed at any age, although golden retrievers appear to be most commonly affected, followed by boxers, bullmastiffs, basset hounds, St. Bernard dogs, Scottish terriers, Airedales, and bulldogs.