Adrenal Gland Cancer (Pheochromocytoma) in Horses
Key takeaways
Adrenal gland cancer (pheochromocytoma; PCC) in horses is a rare form of tumor that arises from the adrenal medulla.
- PCCs are often benign and asymptomatic when the tumor does not produce excessive catecholamines
- Cases with symptoms are rare and related to the production and release of large amounts of epinephrine from these tumors
- The most common symptoms are diarrhea, rapid breathing, excessive sweating, colic, and muscular tremors
- Diagnostic tests include blood work, urine evaluation of catecholamine levels, abdominal ultrasound, and rectal palpation
- These tumors are often identified post-mortem because they are often asymptomatic
- There is no good treatment available for PCC, as surgical removal is often too risky
- Supportive therapy with pain relief and intravenous fluids can be used, but there are no reports of it successfully treating catecholamines-producing PCCs
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A closer look: Adrenal Gland Cancer (Pheochromocytoma) in Horses
The tumor originates from the chromaffin cells in the adrenal gland. These cells normally secrete the catecholamines epinephrine and norepinephrine.
Pheochromocytoma is a rare tumor in horses and most cases of PCCs are benign and asymptomatic.
Catecholamine-producing PCC can be life-threatening and as such should be considered an emergency, especially if symptoms, such as colic, are present.
Symptoms and their secondary effects can lead to acute death and veterinary care must be seeked immediately.
Risk factors
The presence of clinical signs is already an indicator of a heightened severity.
Malignant cases can also present with metastasis to other parts of the body, particularly the brain and lungs.
Death can also occur because of acute hemorrhage due to the tumor rupturing.
Possible causes
As for many cancer types, the causes behind PCC are still largely unknown.
The tumor develops from the chromaffin cells produced in the adrenal medulla, which are responsible for the synthesis and release of catecholamine epinephrine.
Main symptoms
Pheochromocytoma often presents as asymptomatic.
Testing and diagnosis
Given that most adrenal gland tumors present as asymptomatic they are often identified post-mortem.
The diagnostic process for discovering PCC in a live horse includes rectal palpation, bloodwork, evaluation of catecholamines in the urine, and abdominal ultrasounds.
Steps to Recovery
There are no good treatment options for PCCs. Surgical removal is often not performed due to cost and the high risk post-surgical hemorrhage.
Some cases can be managed with pain relief and intravenous fluid therapy, but there are no reports of successful treatment for symptomatic horses with PCC.
The prognosis varies depending on factors such as the stage and the size of the cancer.
Most pheochromocytomas are benign and present without symptoms.
PCCs become a life threatening condition due to the clinical signs. Prognosis following the onset of clinical signs is poor as surgical treatment is often risky and costly and prone to complications such as hemorrhages.
Prevention
As for most tumors, the cause behind adrenal gland cancer is idiopathic (unable to be determined). As such, prevention is not possible.
Pheochromocytoma is not contagious.
Is Adrenal Gland Cancer (Pheochromocytoma) in Horses common?
Pheochromocytoma is rare in horses.
Typical Treatment
- No treatment
- Surgical removal
- Supportive care (IV fluid therapy; pain relief)
