THE term “lymphoma” describes a diverse group of cancers in dogs that are derived from white blood cells called lymphocytes.
Lymphocytes normally function as part of the immune system to protect the body from infection. Although lymphoma can affect virtually any organ in the body, it most commonly arises in organs that function as part of the immune system such as the lymph nodes, spleen, and bone marrow.
By far the most common type of lymphoma in the dog is multicentric lymphoma, in which the cancer first becomes apparent in lymph nodes. Other common lymphomas in dogs include cutaneous lymphoma (lymphoma of the skin), alimentary or gastrointestinal lymphoma (lymphoma of the stomach and/or intestines) and mediastinal lymphoma (lymphoma involving organs within the chest, such as lymph nodes or the thymus gland).
Unfortunately, the cause of lymphoma in dogs is not known. Although several possible causes such as viruses, bacteria, chemical exposure, and physical factors such as strong magnetic fields have been investigated, the cause of this cancer remains obscure.
The most common initial symptom of multicentric lymphoma in dogs is firm, enlarged, non-painful lymph nodes. Other common symptoms include loss of appetite, lethargy, weight loss, swelling of the face or legs, 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.
Dogs with gastrointestinal lymphoma usually have symptoms such as vomiting, watery diarrhoea, and weight loss. The diarrhoea is often very dark in colour and foul smelling. 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 within the chest. Affected dogs may also show swelling of the face or front legs as well as increased thirst and urination.
The most effective therapy for most types of canine lymphoma is chemotherapy. In some cases, surgery or radiation therapy may also be recommended. There are numerous chemotherapy treatment protocols for dogs with lymphoma. Unlike humans, dogs tend not to have severe side effects to chemotherapy. Consult your veterinarian if your pet is unwell.