Lymphoma And Lymphosarcoma
In Your Ferret

Ron Hines DVM PhD 4/29/06

Lymphoma and lymphosarcoma describe the same condition. These common tumors of ferrets are tumors of certain white blood cells called lymphocytes. Lymphocytes come in two different forms, T cells and B cells. T-cells regulate the attack white blood cells of the body while B cells are responsible for circulating antibodies against disease. Next to adrenal gland tumors, lymphomas and lymphosarcomas are the most common tumors I see in ferrets.

Malignant lymphomas and lymphosarcomas are solid lymphocyte tumors that form in the lymph nodes of the body and spleen. From there they can spread to many organs of the body. Ferrets of any age can develop lymphoma/lymphosarcoma but most that do are over four years of age. Male and female ferrets are equally affected. In cats, the immunodeficiency virus is responsible for many cases of lymphoma but we do not know if viruses precipitate this disease in ferrets.

Because so many different organs can be infiltrated with cancerous lymphocytes the disease can have any number of signs and can be confused with many different diseases. Like feline leukemia, it can be the true cause lurking below the surface of almost any signs of ill health in ferrets. Lymphosarcoma occurs in three forms in ferrets. The juvenile form affects ferrets less than two years of age. This is a highly malignant and rapidly progressing form of the disease characterized by large highly malignant (anaplastic) lymphocytes. Since superficial lymph nodes are not often enlarged in this form, the condition is often missed until it is quite advanced. One characteristic sign that may be noted is an enlarged spleen. The spleen can be many times its normal size. When it takes up a significant portion of the abdominal cavity it should be surgically removed. When the liver or intestines are involved, the problem can be confused with digestive disturbances (diarrhea, weight loss, vomission, dehydration) or hepatitis (jaundice and elevated liver enzymes). When the thymus in the anterior chest is enlarged, coughing and gasping may occur. In the adult form of lymphosarcoma, superficial lymph nodes and spleen are usually enlarged. In these older ferrets the disease does not progress as rapidly as it does in younger animals. Later in this disease, the major organs of the body become invaded with neoplastic (cancerous) lymphocytes. Other signs depend on which organs are affected but commonly include loss of curiosity, energy and appetite, weight loss, vomiting and diarrhea. Some animals show paralysis when the nervous system is invaded. Masses are often palpated in the abdomen or seen in x-rays of the chest. When the tumor is present in the chest the respiratory difficulties seen are sometimes misdiagnosed as heart problems or pneumonia. Sometimes circulating lymphocyte numbers are increased. In a third form of the disease, the lymphocytes have become highly rudimentary and highly aggressive and invasive. Dr. Williams, a veterinary pathologist with the AFIP calls this the “immunoblastic-polymorphous variant” and recounts that it is most common in the US Midwest. He is also suspicious that a virus may be implicated in its transmission.

Diagnosis
A definitive diagnosis of this disease requires a biopsy of the affected tissue sent to a pathologist for interpretation. This is often a fine needle aspirate or snippet of an enlarged lymph node or intra-abdominal mass. An increase in circulating lymphocytes noted in a blood test is another common finding. However, the diagnosis of lymphoma/lymphosarcoma should not be based on elevated white blood cell counts alone because a number of infectious diseases also elevate lymphocyte numbers.. Other common blood test findings are anemia, elevated liver enzymes and high serum calcium levels. When the lungs are involved and there is fluid in the chest x-rays can helps make the diagnosis. Lymphoma/lymphosarcoma of the chest can be easily confused with heart problems or pneumonia. An enlarged spleen often accompanies lymphoma/lymphosarcoma but it is also very common in non-cancerous chronic intestinal disease so prevalent in ferrets.

Treatment
Fortunately, lymphoma/lymphosarcoma often responds, at least temporarily, to chemotherapy. Ferrets tolerate chemotherapy quite well and initial improvement can be very dramatic. However consider yourself exceedingly blessed if you gain another 2-5 months time with your pet through these treatments. Please do not feel guilty if you elect not to try them. The most common chemotherapeutic protocols involve the use of prednisone or prednisolone (0.5mg/pound/day orally), vincristine (0.0125-0.025mg/pound, IV,IP) and cyclophosphamide (1mg/pound orally 4 days/wk), cytoxin or doxorubicin (0.5mg/pound IV every 21 days). Other drugs that may be effective is oral Idarubricin (0.25-0.5mg/day) for three days every 21 days or L-asparaginase (200units/pound,IV,IP). With all these drugs, the ferrets white and red cell numbers need to be carefully monitored for myelosuppression and vomiting and lack of appetite and fever can be a problem. Subcutaneous or intravenous fluids, appetite stimulants and antibiotics may be helpful while the ferret is on these medications. Using these drugs it is common for ferrets to live in remission an additional six month to a year. The use of prednisone/prednisolone will sometimes cause the ferret to experience mood changes.

Please remember that these ferrets can be helped but not cured. Treatment is more of a quality of life issue. Some veterinary centers include radiation in their treatment protocols. During treatment, ferrets become more susceptible to infections due to loss of white blood cells. It is important to realize that older ferrets may have other health problems such as adrenal tumors or insulinomas that complicate treatment and lessen its effectiveness. The younger the ferret is when he develops the disease, the more rapid and consuming it tends to be. A common and unfortunate story is the ferret that comes in with few signs other than enlarged superficial lymph nodes. These ferrets respond dramatically to prednisone/prednisolone administration only to be returned a few months later with the disease spread to many internal body organs. Because of this, it is better to include other chemotherapeutic agents in the initial treatment.

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