- Clinical science
A pheochromocytoma is a catecholamine-secreting tumor typically located in the adrenal medulla. Pheochromocytomas are usually benign (∼ 90% of cases) but may also be malignant. Classic clinical features are due to excess sympathetic nervous system stimulation and involve episodic blood pressure crises with paroxysmal headaches, diaphoresis, heart palpitations, and pallor. However, a pheochromocytoma may also present asymptomatically or with persistent hypertension. Elevated catecholamine metabolites in the plasma or urine confirm the diagnosis, while imaging studies in patients with positive biochemistry are used to determine the location of the tumor. Surgical resection is the treatment of choice, but is only carried out once alpha blockade with phenoxybenzamine has become effective.
- Age range: 3rd–5th decades of life
- Present in up to 1% of all hypertensive patients
Epidemiological data refers to the US, unless otherwise specified.
- Tumor arise from chromaffin cells, which are derived from the neural crest. Locations include:
- 25% of pheochromocytomas are hereditary. Associations include:
“10 percent rule”- roughly 10% of pheochromocytomas are: extra-adrenal, multiple, bilateral, malignant, pediatric cases, not associated with hypertension, show calcifications on imaging!
- Episodic hypertension (or persistent hypertension in some cases)
- If is secreted, signs of
- Weight loss due to increased basal metabolism
- Other signs and symptoms consistent with associated familial disorders:
- Whenever possible, all medications should be put on hold one week prior to testing.
- Best initial test: metanephrines in plasma (high sensitivity)
- Confirmatory test: metanephrines and catecholamines in 24-hour urine (high specificity)
Clonidine suppression test (rarely used)
- Principle of the test: In healthy patients, clonidine normally significantly decreases plasma catecholamine levels by at least 30%.
- Evaluation of results: If pheochromocytoma is present, catecholamine levels will fail to decrease upon clonidine administration, as the tumor will continue to produce catecholamines.
- Genetic testing: if MEN2A, MEN2B, NF1, or VHL is suspected
Other diagnostic tests
- 24-hour ambulatory blood pressure monitoring
Adrenal/abdominal CT or MRI (after positive biochemistry tests to localize tumor)
- Scintigraphy (MIBG)
- Other imaging to search for potential additional tumors in patients with pheochromocytoma and MEN2A, MEN2B, NF1, or VHL
Operable disease: Management consists of preoperative blood pressure management and then surgery.
- Preoperative blood pressure management: Combined alpha and beta-adrenergic blockade
Treatment of choice: laparoscopic tumor resection (adrenalectomy)
- "No-touch" technique
- Open surgical resection is reserved for large or invasive tumors.
Prognosis and follow-up
- Over half of all patients with benign pheochromocytoma become normotensive after tumor resection.
- Long-term annual biochemical monitoring for recurrence is indicated in all patients.
- Benign pheochromocytoma recurs in ∼ 15% of patients, usually 5–15 years after surgery
- The prognosis for malignant pheochromocytoma is highly variable
Starting beta blockers before alpha blockade is contraindicated. Beta blockers cancel out the vasodilatory effect of peripheral beta-2 adrenoceptors, potentially leading to unopposed alpha-adrenoceptor stimulation → vasoconstriction → hypertensive crisis.
- Inoperable disease