Lymphoma describes a diverse group of cancers in dogs that are derived from white blood cells call lymphocytes. Lymphocytes normally function as part of the immune system to protect the body from infection. It most commonly arises in organs that function as part of the immune system such as the lymph nodes, spleen and bone marrow. The most common type of lymphoma in dogs is multicentric lymphoma, in which the caner first becomes apparent in the lymph nodes.
Lymphomas represent approximately 7-14% of all cancers diagnosed in dogs. Some progress rapidly and are acutely life threatening without treatment, while others progress very slowly and are managed as chronic, lethargic diseases.
Canine lymphomas are similar in many ways to the non-Hodgkin’s lymphomas (NHL) which occur in humans. Canine lymphomas and NHL are nearly indistinguishable when examined microscopically and both tumor types exhibit similar responses to chemotherapy.
Common symptoms of canine lymphoma
The most common initial symptom of multicentric lymphoma in dogs is firm, enlarged, non-painful lymph nodes. A lymph node affected by lymphoma will feel like a hard, rubbery lump under your dog’s skin. Other common symptoms include loss of appetite, lethargy, weight loss, swelling of the faces or legs (edema) and occasionally increased thirst and urination.
Cutaneous lymphoma tends to appear first as dry, flaky, red and itchy patches of skin anywhere on the body. As it progresses, the skin becomes moist, ulcerated, very red and thickened. Masses in the skin can also occur with cutaneous lymphoma. It may also appear in the mouth, often affecting the gums, lips and the roof of the mouth.
Dogs with mediastinal lymphoma typically have difficulty breathing. This may be due to the presence of a large mass within the chest or due to the accumulation of fluid with the chest (pleural effusion). Affected dogs may also show swelling of the face or front legs as well as increased thirst and urination.
How is canine lymphoma diagnosed?
In addition of biopsy, blood tests, a urinalysis, x-rays, an abdominal sonogram and a bone marrow aspirate are used to determine how far the lymphoma has spread throughout the dog’s body.
How is canine lymphoma treated?
Most dogs tolerate chemotherapy well, actually must better than humans typically do. Generally, fewer than 5% of dogs treated for lymphoma using chemotherapy will experience side effects that need to be managed in a hospital setting. The most common side effects include loss of appetite, decreased activity level and mild vomiting or diarrhea that persists for a day or two.
Unlike people, dogs usually do not lose their hair when treated with chemotherapy. The exceptions to the rule are Poodles, Old English Sheepdogs and some Terriers.