Dogs have numerous lymph tissues that are important in fighting infection and inflammation.
These can be found in the lymph nodes, which are in various locations throughout the body, including the back of the rear leg, behind the jaw, in the front of the shoulder, groin, abdomen, and the area around the heart. In addition, the tonsils, spleen, intestines, and bone marrow are also essential sources of lymphoid tissue. Cancer can develop in these tissues, as with almost any body organ, and this lymphoid cancer is called lymphoma.
In dogs, lymphoma is most commonly associated with middle age. However, it may be more common in certain breeds, including Boxers, Bullmastiffs, German Shepherds, Poodles, and Golden Retrievers.
What does it look like
Signs can be variable, depending on the number and type of lymphoid tissues affected.
Dogs may initially act normally, with the only evidence of illness being an enlargement of one or more external lymph nodes, which feel like firm, walnut-sized round lumps beneath the skin. The abdomen may appear bloated if there is extensive involvement of abdominal organs, such as the spleen. Dogs with the involvement of the intestinal tract may have vomiting and diarrhea, loss of appetite, and weight loss. Involvement of the chest can lead to breathing difficulty and heart problems.
How is it diagnosed
Diagnosis may require various tests, including blood tests, x-rays, ultrasound, and needle aspiration of affected lymph nodes.
In the latter procedure, a needle and syringe are used to draw cells from the enlarged nodes; these cells are then examined under a microscope for malignant characteristics. Sometimes, an entire lymph node may need to be removed to confirm the diagnosis.
How is it treated
Lymphoma generally responds well to chemotherapy, usually with a course of treatment involving multiple oral and injected drugs.
Approximately 75% of treated dogs and about 50% of treated cats go into complete remission for six months or longer. In addition, the chemotherapy doses used in dogs are lower than those used in people, so most dogs do not lose hair or have treatment-related severe illnesses. However, setting up the proper chemotherapy protocol requires specialized expertise, so your veterinarian may refer you to a teaching hospital or specialty practice.
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