What is Lymphoma?

Lymphoma, also known as Lymphosarcoma, is a malignant cancer that is affecting our canine companions. This type of cancer involves the lymph system including the lymph nodes and sometimes the liver and spleen. Middle aged to older dogs of either sex are potential victims of this disease. Lymphoma in cats can be related to the feline leukemia virus but there isn't any conclusive evidence that a viral cause exists for the dog. A possible genetic predisposition may exist though that could explain why this cancer is seen more in particular breeds. Cancer in any form is an unregulated growth of cells. Something causes the individual cells to divide the wrong way creating an abnormal growth which takes over the normal tissue disrupting the function of the tissues and organs. When the normal functions can't continue, the animal becomes sick and the body's ability to perform required tasks rapidly declines.

Lymphoma can present itself in several different ways involving different areas of the lymph system. The most common form in the dog is multicentric (several sites in the body). The peripheral (around the outside of the body) lymph nodes are affected in this form. These lymph nodes are usually difficult to feel under the skin but when affected by Lymphoma these lymph nodes are enlarged and are easy to notice. Owners can usually feel enlarged lymph nodes below the angle of the jaw, in front of the shoulder blades, behind the knees, and under both the front and back legs where they join the body. The enlarged lymph nodes at the jaw can make the dog's face become swollen and this can be the first abnormal sign noticed. Sometimes these lymph nodes are not easy to feel and the first thing owners detect is a lack of energy in the dog along with a decreased appetite, possible weight loss, increased thirst and increased urination. This multicentric form can eventually involve the liver and spleen in the abdomen.

Other types of Lymphoma include alimentary, mediastinal, cutaneous and extranodal. During alimentary Lymphoma, which involves the stomach and the intestines, the dog will usually experience vomiting and diarrhea, weight loss and lethargy. Mediastinal Lymphoma causes a growth of cancer in the front part of the chest leading to fluid in the chest and difficulty breathing. Cutaneous Lymphoma affects the skin and is uncommon. Extranodal Lymphoma is a combination of other potential sites in the body that can be affected with this form of cancer. These include the eyes, the central nervous system (the brain and the spinal cord), bones, heart, kidneys, bladder and the nasal cavity.

Any type of cancer carries with it a grave prognosis. Lymphoma can be treated with chemotherapy and is probably the most commonly treated cancer in dogs because the chemotherapy protocols are well established and the chances of a good response to the chemotherapy are favorable. The dreaded statistics are that an untreated dog will most likely die from its disease within four to six weeks. With a combination chemotherapy there is an eighty-four percent chance of remission (making the cancer seem to disappear for a period of time) and the average survival time of the dog when treated is 357 days. The average duration of remission is 252 days.

If the patient comes out of remission, a second remission can be induced, but is usually only one-half the length of the first remission. The bottom line is that a dog can be treated with this form of cancer but it can be costly. A large number of treated dogs do very well with treatment and can live a relatively normal life for close to another year. We do have to remember that one year in a dog's life is like six to seven years in ours.

What are the symptoms of lymphoma?

The symptoms of lymphoma are related to the location of the tumor(s). Tumors that develop in the lymph nodes often present as swellings with no other symptoms. The gastrointestinal form often is accompanied with vomiting, diarrhea, weight loss, and lack of appetite. The mediastinal (chest) form often presents with shortness of breath and muffled heart sounds. The cutaneous (skin) form can present in several different ways including single or multiple lumps in the skin, or mouth. These bumps can itch or be red and ulcerated.

What is the treatment for lymphoma?

The treatment for lymphoma in the dog consists of chemotherapy. Lymphoma is considered a systemic disease, which makes surgery and radiation impractical and ineffective. There is a wide variety of chemotherapy protocols and drugs that are currently being used to treat lymphoma. The treatment usually consists of a combination of oral and injectable drugs given on a weekly basis. Some commonly used drugs include cyclophosphamide, vincristine, doxorubicin, and prednisone. The exact treatment protocol will vary depending on the practitioner. The University of Wisconsin protocol is one of the more popular ones used by veterinary oncologists. While most veterinarians can administer the treatment protocols, it should be noted that the owners of a dog with lymphoma initially should seek out a consultation with a veterinary oncologist to inform themselves of any new treatment recommendations.

What is the long-term outlook for a dog with lymphoma?

Some owners choose not to treat dogs that develop lymphoma. The life expectancy of these untreated dogs averages 4 to 6 weeks. Oral prednisone therapy may reduce the swellings and discomfort, but probably will not appreciably extend their life span. It must also be noted that oral prednisone treatment prior to chemotherapy is not recommended and may actually reduce the effectiveness of the chemotherapy.

In dogs that do undergo one of the recommended chemotherapy protocols, life expectancy can extend out to a year and occasionally longer. However, even dogs that receive appropriate chemotherapy usually do not live longer than a year. If a dog tolerates chemotherapy (most dogs do) their quality of life can be quite good during the treatment period. Treatment for lymphoma in the dog is considered one of the more successful cancer treatments and can often be performed by a local veterinarian without the need to travel long distances to veterinary schools or specialty clinics.