Adrenal Cortex Tumors

What are the adrenal glands and adrenal cortex?

The adrenal glands are a pair of glands located above each kidney. The adrenal glands have an outer cortex that 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 cortex is responsible for producing cortisol, the ‘stress’ hormone, and is important in body metabolism.

What is an adrenal cortex tumor?

An adrenal cortex tumor is an abnormal growth of cells in the adrenal cortex. It can be malignant (adenocarcinoma) or benign (adenoma). In both cases, it can cause Cushing’s disease (hyperadrenocorticism) because the tumor can lead to an overproduction of certain body hormones.

What causes this type of tumor?

The reason 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 adenocarcinomas, there are no known causes.

What are the clinical signs of adrenal cortex tumors?

Excess production of the adrenal hormones may cause pets to have signs such as increased drinking and urination, hair loss, and a pot-bellied appearance. This is due to Cushing’s disease (see handout “Cushing’s Disease in Dogs” for more information). Dogs with adrenal cortex tumors often experience muscle weakness, causing listlessness, lethargy, and weight gain.

Other signs may include calcium deposits in the skin (calcinosis cutis) and muscle wasting. Many dogs only exhibit a few of these signs. Weight loss may occur if a condition secondary to the excess hormone develops, such as diabetes mellitus.

How is this cancer diagnosed?

If your pet is exhibiting the signs described above, your veterinarian may suspect an adrenal cortex tumor and further evaluation with blood and urine testing and abdominal ultrasound will help to confirm the diagnosis. Your veterinarian must determine if your pet’s signs are caused by an adrenal cortex tumor or if your pet has pituitary-dependent Cushing’s disease (meaning a tumor in the pituitary gland is causing the adrenal cortex to overproduce cortisol).

In some cases, a tumor (usually adenocarcinoma) will be present in only one of the adrenal glands. In pituitary-dependent disease, since both adrenal glands are stimulated by the pituitary gland, both adrenal glands are usually enlarged.

A CT scan, MRI, or ultrasound may be recommended.

How does this cancer typically progress?

In most cases, especially in dogs, these tumors are benign. The mass may continue to grow and your pet may continue to exhibit clinical signs. This will be detrimental to the long-term health of your pet. Benign tumors do not spread to other areas of the body.

In the malignant form, the tumor may invade the surrounding tissues and blood vessels. This can lead to severe complications, including weakness and the development of thrombi (blood clots) in vessels that cut off blood supply, making surgical removal more difficult and complicated. These tumors can metastasize (spread) to other organs, including the kidneys, lymph nodes, and thyroid gland.

What are the treatments for these types of tumors?

Surgical removal of the affected adrenal gland is generally the most effective treatment; however, medical therapy may be used instead depending on your pet’s health status.

"The most common treatment for benign forms of this disease is medical (drug) therapy."

The most common treatment for benign forms of this disease is medical (drug) therapy. Medical therapy aims to inhibit the hormone pathways from the pituitary gland to the adrenal glands or against the adrenal gland tissue itself, either by destroying adrenal cells using mitotane (Lysodren®) or blocking hormone production from the gland using trilostane (Vetoryl®). Given that adenomas are more common than adenocarcinomas, this therapy is appropriate; however, if malignancy is suspected, surgery may be recommended instead of medical therapy.

Prior to surgery, staging (searching for potential spread to other locations in the body) is recommended for malignant tumors. This may involve blood work, urinalysis, radiographs (X-rays) of the lungs, and possibly an abdominal ultrasound, MRI, or CT scan.

Is there anything else I should know?

By far, the most common tumors that affect pets’ adrenal glands are benign in nature. However, even benign tumors can cause health complications due to tumor growth. The sooner a diagnosis and treatment plan can be determined, the better the outcome for your pet.

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