What are the adrenal glands? And what is the adrenal medulla?The adrenal glands are a pair of glands located above each kidney. The adrenal glands have an outer cortex which is responsible for producing many chemicals (hormones) that influence certain organs and metabolic activities in the body. The inner part of the adrenal gland is called the medulla. The adrenal medulla is responsible for producing hormones such as epinephrine, norepinephrine, and dopamine. These hormones have various roles in the body; for example, epinephrine and norepinephrine affect heart rate and blood pressure.
The cells that create these hormones are called chromaffin cells.
What is an adrenal medulla tumor?A malignant form of this tumor is called pheochromocytoma and involves abnormal growth of these chromaffin cells in an uncontrolled way that causes the formation of a tumor.
Adrenal medulla tumors occur in 1-2% of dogs and less than 1% of cats.
What causes this type of tumor?The reason why a particular pet may develop this, or any tumor or cancer, is not straightforward. Very few tumors and cancers have a single known cause. Most seem to be caused by a complex mix of risk factors, some environmental and some genetic or hereditary.
In the case of pheochromocytomas, there is no known cause.
What are the signs of these types of tumors?These tumors may go undetected for an extended period of time and signs may be subtle. These signs could include weakness or collapse, excessive panting and restlessness, newly noted anxiety, and an increase in drinking and urination. Anxiety, restlessness, weakness/collapse, in combination with episodes of high blood pressure and an elevated heart rate, would prompt your veterinarian to investigate further if revealed during a wellness exam.
How is this cancer diagnosed?Diagnosing these tumors can be difficult, especially without advanced imaging, including MRI and CT scans. Patients are usually older dogs with episodes of clinical signs related to the release of the hormones epinephrine and norepinephrine. If your pet has been exhibiting signs as described above, your veterinarian may recommend an abdominal ultrasound. These tumors are sometimes diagnosed via ultrasonography of the abdomen, although more advanced imaging (MRI and CT scans) is often required.
How does this type of tumor typically progress?The biggest concern with these tumors is their ability to continue to grow and invade local tissues. There are large blood vessels in the abdomen closely associated with these glands. If a large portion of the tumor invades one of these vessels, it can make surgical removal difficult or impossible.
Spread (metastasis) has been noted in up to 40% of dogs with pheochromocytomas and is an additional concern. Staging (searching for potential spread to other locations in the body) is highly recommended. This may include bloodwork, urinalysis, X-rays of the lungs, and abdominal ultrasound.
What are the treatments for this type of tumor?The most commonly pursued treatment for these tumors is surgery. CT scans of the abdomen are usually required prior to surgery to determine if the tumor has invaded any local blood vessels that could make surgery difficult or dangerous for your pet. To reduce potential complications associated with the periodic release of hormones, medications to control hypertension or heart arrhythmias may be prescribed ahead of surgery.
Is there anything else I should know?These tumors are generally treatable when small and your pet can have an excellent quality of life afterward.

This client information sheet is based on material written by Christopher Pinard, DVM© Copyright 2018 LifeLearn Inc. Used and/or modified with permission under license.