Endocrine Abstracts

Introduction: With the advent of modern imaging, up to 30% of adrenal pheochromocytomas are discovered incidentally in asymptomatic patients. Smaller tumors may be ‘pre-biochemical’ in their secretory capacity, but truly nonfunctioning tumors over 3 cm are exceedingly rare. We describe a case of a clinically and biochemically silent pheochromocytoma.

Case report: A 65-year-old woman was found to have a left adrenal incidentaloma on an abdominal CT carried out during hospitalization for acute pyelonephritis. The mass was 3.5 cm in diameter and displayed an imaging phenotype consistent with pheochromocytoma. The tumor was also positive on ¹²³I-MIBG scintigraphy. The patient’s history was notable for arterial hypertension controlled on telmisartan 40 mg/d and mixed hyperlipidemia on simvastatin 40 mg/d. She had a parathyroid adenoma removed in the past. Biochemical evaluation showed a normal overnight dexamethasone suppression test, normal plasma aldosterone/plasma renin activity, normal 24 h urine total metanephrines and VMA. Urinary dopamine was not tested. The patient underwent a laparoscopic left adrenalectomy without preoperative preparation and no perioperative complications. Histology was complatible with a neoplasm of the adrenal medulla, consisting of cells with granular oxyphil cytoplasm and regular nuclei, positive to chromogranin A and CD56 and negative to inhibin and melan A and nearly undetectable Ki-67.

Conclusion: Pheochromocytomas are recognized by their imaging characteristics in asymptomatic patients and although varying in their secretory patterns, tumors >3 cm are rarely nonfunctioning. These tumors should still be best managed by resection following adequate α-blockade.