Ferrets - Tumors
Ferrets can suffer from tumors in any part of their body, ranging from benign cancers of the skin to aggressive malignant tumors of internal organs. A large number of ferrets are affected by tumors of the lymphoid system and the pancreas. This handout will discuss only these two tumors; information about tumors of the skin may be found in the handout, Ferrets - Skin Diseases.
What is lymphoma?
Lymphomas are tumors of the lymphoid (immune) system and can affect all ages of ferrets (the most common age range is 2 - 9 years).
"Malignant lymphoma and lymphosarcoma are the most common malignancy seen in ferrets."
Malignant lymphoma and lymphosarcoma are the most common malignancy seen in ferrets. Lymphomas can affect the lymph nodes, liver, spleen, respiratory system, bone marrow, gastrointestinal tract, eyes, skin, nervous system, heart and kidneys. The clinical signs depend on the type of tumor, organ involved and the stage of the disease. Ferrets may be asymptomatic for years.
How is lymphoma diagnosed?
Anorexia, lethargy, weight loss, depression, vomiting, diarrhea, blood in the feces, abdominal distention, bulges or visible masses, palpable masses (masses that can be felt by an experienced examiner such as a veterinarian), problems breathing, coughing and hind limb weakness may occur. This diversity of signs can make diagnosis difficult. A blood sample with a high number of lymphocytes, especially if the lymphocytes have certain specific characteristics, may be diagnostic.
In adult ferrets, enlargement of lymph nodes is an important sign as is enlargement of the spleen, although the spleen can enlarge without tumors being present. A biopsy of lymph node or suspected tumor (mass) provides the definitive diagnosis.
What is the treatment for lymphoma?
For a dedicated owner with a compliant patient, surgery and/or treatment with chemotherapy is an option. Adjunctive or supportive treatment with antioxidants and immune stimulating supplements may improve the outcome.
What is insulinoma?
Tumors of the pancreas involving the beta cells, which produce insulin, are surprisingly common in ferrets. The tumor, called an insulinoma, may be an insulin-producing adenoma or an insulin-producing adenocarcinoma. By definition, an adenoma is benign, while an adenocarcinoma is malignant. The average age for a ferret to develop an insulinoma is 5 years old, but it may be seen as early as 2 years of age.
Insulin reduces blood sugar; an increase in this hormone, as produced by an insulinoma, results in dangerously low levels of glucose in the blood. The results of these low levels of blood glucose are manifest on the brain (nervous system) and the adrenal gland.
Clinical signs include pawing at the mouth, "stargazing", weakness (often seen in the hind end), tremors, collapse, abnormal behavior, depression, lethargy, and confusion. The symptoms can progress to include seizures and hypoglycemic (low blood sugar) coma. The adrenal gland reacts to precipitous reductions in blood glucose by producing adrenaline; increased levels of adrenaline cause a rapid heart rate, tremors and irritability. On the other hand, some ferrets with tumors of the pancreas show no obvious clinical signs or may show only intermittent signs; a ferret that has only intermittent episodes of hypoglycemia may go undetected because these symptoms are not always witnessed.
How is an insulinoma diagnosed?
"All too often ferrets with insulinomas have normal insulin levels at the time of sampling."
A measurement of the blood insulin level would seem to be the obvious test, but all too often ferrets with insulinomas have normal insulin levels at the time of sampling. The ratio of insulin to glucose is a more useful test. If there is a high level of insulin in the face of a low glucose level, the diagnosis is definitively made. Often a diagnosis is made based upon clinical signs and absence of other abnormalities on the physical examination or blood testing.
How is insulinoma treated?
Treatment of insulinomas may be medical or surgical, depending on the severity of the disease and the age of the ferret. Medical therapy involves use of a corticosteroid like prednisone and/or a drug like diazoxide to increase blood glucose levels. These medicines do not stop the progression of the tumor, but will minimize the clinical signs. Surgery remains the treatment of choice and involves removing any visible pancreatic tumor nodules. It is important to recognize that while, it is easy to remove visible nodules, this disease often has microscopic lesions and surgery is not always curative.
"Surgery remains the treatment of choice."
Diet must also be managed. Ferrets tend to be "grazers" or nibblers when they eat. Therefore, it is preferable to provide numerous small meals daily to provide a more consistent food intake, which helps level out the blood glucose levels.
If a ferret experiences a sudden collapse or a hypoglycemic coma, emergency treatment is critical for its survival. Immediately rub honey or corn syrup onto the gums (be careful if the ferret is seizuring, as there is a danger of being bitten.) Then, rush your ferret to the veterinarian, who will administer an intravenous drip containing a 50% dextrose solution to treat the other symptoms of hypoglycemia.
What is the prognosis?
Surgical treatment to remove the tumors is the optimal therapy and the largest reported series of cases to date demonstrated a mean survival time after surgery of around 500 days, which is relatively long given that these are generally middle-aged ferrets. Many ferrets respond to medical therapy and depending upon the severity of the disease can live for several months up to several years.