Pheochromocytoma: An Incidental Finding in an Asymptomatic Older Adult With Renal Oncocytoma

Pheochromocytoma is a rare catecholamine-secreting tumor of chromaffin cells of the adrenal medulla or sympathetic ganglia, occurring in about 0.2 to 0.5% of patients with hypertension.^1-3 However, in a review of 54 autopsy-proven cases of pheochromocytoma, about 50% of the patients with hypertension were not clinically suspected for pheochromocytoma.⁴

Pheochromocytoma is usually diagnosed based on symptoms of hyperadrenergic spells, resistant hypertension, especially in the young, with a pressor response to the anesthesia stress test and adrenal incidentaloma.

The classic triad of symptoms associated with pheochromocytoma includes episodic headache (90%), sweating (60-70%), and palpitations (70%).^2,5 Sustained or paroxysmal hypertension is the most common symptom reported in about 95% of patients with pheochromocytoma. Other symptoms include pallor, tremors, dyspnea, generalized weakness, orthostatic hypotension, cardiomyopathy, or hyperglycemia.⁶ However, about 10% of patients with pheochromocytoma are asymptomatic or mildly symptomatic.⁷ Secondary causes of hypertension are usually suspected in multidrug resistant or sudden early onset of hypertension.⁸

Approximately 10% of catecholamine-secreting tumors are malignant.^9-11 Benign and malignant pheochromocytoma have a similar biochemical and histologic presentation and are differentiated based on local invasion into the surrounding tissues and organs (eg, kidney, liver) or distant metastasis.

A high index of suspicion is necessary during the workup of secondary hypertension as untreated pheochromocytoma may lead to significant morbidity and mortality, especially in patients who require surgical treatment.^4,12 Multiple cases of hypertensive crisis, pulmonary edema, cardiac arrhythmia, and cardiogenic shock are reported in undiagnosed patients with pheochromocytoma undergoing both adrenal or nonadrenal surgery who were not medically prepared with α- and β-adrenergic antagonists and fluids before surgery.^13,14

A typical workup of a suspected patient with pheochromocytoma includes biochemical tests, including measurements of urinary and fractionated plasma metanephrines and catecholamine. Patients with positive biochemical tests should undergo localization of the tumor with an imaging study either with an adrenal/abdominal magnetic resonance imaging (MRI) or computed tomography (CT) scan. If a patient has paraganglioma or an adrenal mass > 10 cm or negative abdominal imaging with a positive biochemical test, further imaging with an iobenguane I-123 scan is needed (Figure 1).

In this article, we present an unusual case of asymptomatic pheochromocytoma in a patient with right-sided renal oncocytoma who underwent an uneventful nephrectomy and adrenalectomy.