Adrenal Gland Cancer (Pheochromocytoma) in Dogs

Your dog’s adrenal gland has two unique areas, which are the inner medulla and the outer cortex. The cortex has several layers that create and distribute three chemicals, androgens, glucocorticoids, and mineralocorticoids (aldosterone). What makes this type of cancer even more dangerous is the rate of speed with which it spreads to other organs. This happens due to the fact that the adrenal gland has a direct route through lymph nodes for distributing hormones, and cancer cells are able to be distributed right along with them. The cause of pheochromocytoma is not known yet, although some veterinary medical professionals believe that exposure to toxins or other chemicals may be a contributing factor.

Adrenal gland cancer (pheochromocytoma), which are endocrine tumors that come from the chromaffin (neuroendocrine) cells in the adrenal gland, are not common in dogs. Pheochromocytoma can cause an increase of hormones, which include epinephrine, aldosterone, and cortisol. These hormones cause symptoms that are like those that happen when your dog is stressed, only these can happen at any time, no matter whether your dog is stressed or not. Just like many other cancers, pheochromocytoma is most common in older dogs, and the average age of those with pheochromocytoma is about 10 years old.

The symptoms of pheochromocytoma may not be noticeable in many dogs, because they are mild, intermittent, and can be mistaken for many other diseases and disorders. Some of the most common are diabetes, renal disease, hyperadrenocorticism, and hepatic disorders. Clinical symptoms that are most often noticed are:

• Abdominal distention
• Acute blindness 
• Anorexia
• Anxiety
• Collapse
• Confusion
• Depression
• Diabetes
• Diarrhea
• Dry skin
• Excessive thirst and urination
• Irritability
• Lethargy
• Loss of hair
• Lumps on neck and back from calcium deposits
• Nervousness
• Nosebleeds (epistaxis)
• Pacing
• Panting
• Restlessness
• Seizures
• Shaking
• Vomiting
• Weakness
• Weight loss

As with many cancers, studies are underway to try and unravel the mystery of this disease, which can be so detrimental to the health of humans and animals alike. Presently, the cause of pheochromocytoma is not known, although some experts believe it has something to do with exposure to toxins or chemicals.

Your veterinarian will do a physical examination of your dog that includes body temperature, weight, height, heart rate, respirations, blood pressure, and reflexes. He will do some neurological tests to see if your dog’s sensory and motor skills are normal, as well as balance, coordination, and cognition. Laboratory tests, such as complete blood count, blood chemistry profile, glucose levels, urinalysis, and fecal examination.

Your dog’s medical history is usually needed to inform the veterinarian of any illnesses or injuries your dog has had, and if his immunizations are up to date. Be sure to let him know if there has been any strange behavior or change in appetite. A fine needle aspiration will be done if it is possible to remove cells from the tumor for analysis. This will let the veterinarian know if the tumor is cancerous. An MRI, ultrasound, CT scan, and x-rays will be done to determine the areas affected by the tumor and to see if it has spread.

Since pheochromocytomas usually occur with other medical disorders, the veterinarian will want to treat the one that is the most serious first. Some of these are pulmonary edema, heart attack, cerebral hemorrhage, extreme increase in blood pressure, and heart failure. Treatment for pheochromocytomas includes removal of the adrenal gland and nearby lymph nodes. If it cannot be removed with surgery because of other illness or age, medications such as Lysodren can be used. However, this drug may also have serious side effects, so the veterinarian may choose to keep your dog under observation for the first 24 hours. The surgery to remove the adrenal gland is complex and has many possible complications, such as severe spikes in blood pressure and pulmonary embolism. Some other critical side effects of surgery may include electrolyte imbalances, hemorrhage, and pancreatitis.

The best treatment for any kind of tumor is surgical removal, but sometimes that is not an option. Sometimes, it may be necessary to remove the gland as well as the tumor, in which case your dog will need medication indefinitely to regulate his hormones. In some cases, the tumor may be unable to be removed, such as when it has integrated itself into a vital organ or if it has already metastasized. In these cases, chemotherapy may be suggested if your dog is in relatively good health, but these tumors are hard to treat with chemotherapy alone.

If the tumor is small and has not spread, the veterinarian may decide to use radiofrequency ablation (RFA) to kill the cancer cells. This procedure is done by sending a current of high temperature through a tiny needle into the tumor, which has been very successful in the past, and is less invasive than surgery.

If your veterinarian is able to remove the entire tumor without damaging the endocrine glands, the chances of your dog’s survival is excellent although there is a chance that the tumors may recur. If you and the veterinarian are able to catch it early enough, another treatment can virtually eliminate the chances of a recurrence. Be sure to follow up with your veterinarian regularly and contact him if there are signs of the tumor returning.