Lymphoma, one of the four major types of cancer, is a neoplasm (an abnormal growth that serves no purpose) of the lymph tissue. It is commonly known as lymph cancer and is almost always malignant. Lymph cancer usually occurs in middle aged dogs, and one of the major indications is the prevalence of one or more lumps just under the skin. Physical examination would normally reveal that the peripheral lymph nodes are enlarged and firm.
While there is no evidence of a link between the leukemia virus and canine lymphoma, feline cancer of the lymphatic system is normally associated with the leukemia virus. The fact that lymphoma is more prevalent in certain breeds is indicative of a genetic predisposition for this type of cancer. Besides this, like all other types of cancers, there is no known cause for lymph cancer in dogs.
The most common form of lymphoma is multi-centric; therefore it appears at several sites at the same time. In normal conditions, lymph nodes are difficult to feel under the skin. The indication of lymph cancer comes in the shape of enlarged lumps that can be felt easily under the skin. In some cases the symptoms of lethargy, loss of appetite, increased thirst and urination and loss of energy appear before the lumps can be felt. Multi-centric lymphoma can potentially spread to the liver and demonstrate the symptoms of liver cancer in dogs.
Other types of lymphomas present different symptoms:
- Lymphoma in the alimentary canal is associated with diarrhea, vomiting, weight loss and lethargy. Cutaneous lymphoma is rare and affects the skin.
- Lymph cancer in the mediastina, the part of the thoracic cavity between the lungs that contains the heart, aorta, esophagus, trachea and thymus, shows as a tumor in the front part of the chest leading to fluid retention and a difficulty in breathing.
- Extra-nodal lymphoma pertains to other parts of the body including eyes, the central nervous system, bones, heart, kidneys, bladder and the nasal cavity where the lymphatic system can be potentially affected by cancer cells.
Aspirates from the lymph nodes are sent to the pathological lab to establish the malignancy of the lumps. Blood tests, X-rays and a biopsy of the lymph tissues are some of the other tests that may be performed for an effective diagnosis.
Without treatment, lymph cancer results in the death of the dog within four to six weeks. Chemotherapy protocols are well defined for treating lymphomas as they are the most commonly treated cancer in dogs. Most dogs respond favorably to anti-cancer drugs, and there is an approximately 84% chances of remission and an increase in the survival time.
Although the overall prognosis of lymphoma is poor, drugs can induce remission. If money is not a consideration, another round of drugs can be administered for a second remission. Even a one year increase in the life of the dog is worth the expense especially if you keep in mind that that one year is equivalent to six to seven years in a dog’s life.