|Adrenal Gland Tumors in Cats and Dogs
|What are adrenal gland tumors?
The adrenal glands are small glands buried in fat in the front of each kidney whose function is to regulate the synthesis of
important hormones such as cortisol, aldosterone and epinephrine. These hormones interact with many other hormones
and influence the function of many organs in the body. Adrenal glands are made up of two major parts, the cortex and the
medulla, both of which can develop malignant disease.
The adrenal glands are located just atop the kidney
How common are adrenal gland tumors?
Based on available data, it is estimated that approximately 0.17%-0.76% dogs (representing 1-2% of all dog tumors) and
0.03% cats (representing 0.2% of all cat tumors) develop primary adrenal gland tumors. Metastasis to the adrenal glands
from other organs is uncommon but when it does occur, lymphoma seems to be the most common cancer to spread to
adrenal glands. Other cancers that spread to this organ include melanoma, pulmonary carcinoma, histiocytic sarcoma,
mammary carcinoma, and hemangiosarcoma. To read about adrenal gland cancer in ferrets, please click here (www.
What are the symptoms and how are adrenal gland tumors diagnosed?
Abnormalities in adrenal glands can be detected by advanced imaging techniques such as CT and MRI scans or
abdominal ultrasounds. Further tests may involve endocrinologic testing, cytology, blood chemistry panel, and imaging of
the abdomen and thorax (chest) to rule out cancer in other sites.
Most adrenocortical tumors in dogs and cats are functional but produce increased levels of a hormone called
glucocorticoid that lead to Cushing's syndrome. This condition causes changes in the blood glucose levels, electrolyte
levels, blood pressure and increases the tendency for blood to clot, leading to an increase in pulmonary embolisms. Some
dogs will have only one of the following symptoms, while others may have many:
Adrenal medullary tumors (pheochromocytomas)
Adrenal medullary tumors are uncommon in dogs and rare in cats and can be distinguished form adrenocortical tumors by
immunohistochemistry. These tumors produce increased levels of catecholamines and are typically diagnosed in older
dogs. Their symptoms can be quite nonspecific:
Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role in
educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets is to
prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.
To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the Cancer Pain Management section.
How important is nutritional support for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for example,
some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).
Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need to
be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more, please
visit the Cancer Nutrition section.
How are adrenal gland tumors treated?
Treatment of adrenal gland tumors will depend on several factors and must be put in the context of all of the pet's medical
problems and overall condition. The treatment options are either surgical removal of the tumor-stricken adrenal gland or
administration of drugs to control the clinical symptoms caused by the tumor. The surgery is technically a very difficult one,
with many potential complications during and after the procedure. After surgery, animals often need to be supplemented
with steroids normally produced by the adrenal gland until the remaining adrenal gland begins to function again. Some
pets will require supplementation for life. If surgery is not an option (eg for pets with inoperable tumors or who are very sick
and/or old), the adrenal gland tumors can be treated by drugs such as Lysodren or ketoconazole.
What are the risks associated with treatment?
Risks associated with surgical treatment of adrenocortical tumors
Urinary tract infections are extremely common in patients with Cushing's disease and these can lead to postsurgical
complications if the stress of the surgery allows the infections to get out of hand. In addition, if only one adrenal gland is
affected, the increased production of cortisols from this gland tends to make the other adrenal gland atrophy (waste away),
so that it will not function well when the cancerous gland is removed. The greatest postsurgical risks for these tumors are
sudden drops in plasma cortisol levels and pulmonary embolism. Other possible surgical complications are hemorrhage
during surgery and postoperatively, electrolyte imbalances, pancreatitis from blood clots or manipulation of the pancreas
Risks associated with surgical treatment of pheochromocytomas
Pheochromocytomas also cause disturbances in electrolyte levels, increases in blood pressure (sometimes life threatening
with or without surgery) and increased tendency for blood clotting to occur. These tumors will release substances
(catecholamines) when manipulated that make all of these problems significantly worse, making them an even greater
surgical risk. The major complications with these tumors are severe spikes in blood pressure and pulmonary embolisms.
The other complications include pancreatitis, hemorrhage and electrolyTe imbalances.
Risks associated with drug treatment of adrenal gland tumors
Complications during treatment with Lysodren can include the development of signs due to decreased cortisol production
from the adrenal glands. These signs, which can be severe and life-threatening if they go unrecognized, include weakness,
lethargy worse than that prior to treatment, loss of appetite, vomiting, diarrhea, and in severe cases, collapse or even
shock. The main side effect of ketoconazole is the potential to cause injury to the liver.
How do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "Locate a veterinary oncologist" section.
Are there any clinical trials evaluating new treatments for adrenal gland tumors in cats and dogs?
There are no available clinical trials investigating new treatments specifically for adrenal gland tumors in pets. However,
there are several clinical trials available for cats and dogs with any tumor type for which your pet may qualify. To learn
more these trials (which are partially or fully funded by the institutions), please visit the Dog Clinical Trials (any tumor type)
or Cat Clinical Trials (any tumor type) section.
To learn more about veterinary clinical trials in general, please visit the Pet Clinical Trials section.
What is the prognosis for pets diagnosed with adrenal gland tumors?
Patients without metastatic disease (spread to other organs) often enjoy long-term survival. Approximately 20% of
adrenocortical tumors can invade surrounding veins, causing potentially life-threatening intra-abdominal or retroperitoneal
(space behind the abdomen) bleeding. Up to 50% of adrenocortical tumors metastasize (spread) to other organs, namely
to the liver and lungs. Other organs may include the kidneys, ovaries and thyroid gland. Up to 50% of dogs with
pheochromocytomas develop concurrent malignancies.
1) Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
|PET CANCER CENTER
Comprehensive guide to cancer diagnosis and treatment in cats and dogs