Pheochromocytoma

General Considerations

• Rare, catecholamine-secreting, neuroendocrine tumor usually found in medulla of the adrenal gland originating in the chromaffin cells
  • Extra-adrenal tumors called paraganglioneuromas
• Most often produces epinephrine and norepinephrine (mostly) which is unregulated by any feedback mechanism
  • Sometimes dopamine is secreted
• About 10 % are malignant
• Occur at any age with peak in 3^rd-5^th decades, equal frequency in both sexes
• Locations of extra-adrenal pheochromocytomas include the organ of Zuckerkandl which is close to the origin of the inferior mesenteric artery, bladder wall, heart, mediastinum, and carotid and glomus jugulare bodies

Clinical Findings

• Headaches, palpitations and diaphoresis with hypertension, frequently episodic
• Weakness
• Nausea
• Tremors
• Anxiety
• Weight loss
• Plasma metanephrine measurements are most sensitive but have lower specificity
• Twenty-four hour urine collection for creatinine, total catecholamines, vanillylmandelic acid and metanephrine has a lower sensitivity but higher specificity

Imaging Findings

• Over 90%  located in adrenal, 98% in abdomen
• Imaging studies are performed after the diagnosis is made on a biochemical basis
• MRI is the preferred study
  • Hyperintense on T2-weighted images
  • No contrast required
• CT scanning
  • Most have a pre-contrast attenuation >10 HU
  • Contrast was  thought to add the risk of inducing hypertensive crisis but no increased risk has been shown with low-osmolar contrast
  • Most lesions vigorously contrast-enhance (>80 HU) and have less than 60% washout of contrast on delayed images
• PET scans have also proved helpful in finding the lesions

Differential Diagnosis

• Adrenal adenomas
• Adrenal carcinomas
• Adrenal metastases

Associations

• Von-Hippel Lindau disease
• Neurofibromatosis
• Multiple endocrine neoplasia (MEN) 2A (Sipple syndrome) and 2B
• Tuberous sclerosis
• Sturge-Weber syndrome

Treatment

• Surgical resection of the mass is the treatment of choice
• Medical treatment is generally used pre-operatively, for management of the hypertensive crises and for treating metastatic disease, if present

Complications

• Cardiac arrhythmias
• Pulmonary edema
• Dilated cardiomyopathy
• Hypertensive encephalopathy
• Stroke

Pheochromocytoma. Pre-contrast axial CT of abdomen shows a mass in the right adrenal gland (white arrow) The left adrenal gland is normal (yellow arrow). Following intravenous contrast (lower photo), the right adrenal mass enhances brightly (red arrow).
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