P050 Pitfalls in Establishing the Diagnosis of Pheochromocytoma Illustrated by Three Case Reports

Background and Objective: Pheochromocytoma is a rare cause of secondary hypertension. Because of the low incidence, any diagnostic test has a low positive predictive value. Methods: We report three example cases with diagnostic pitfalls. Results: First case: A 72-year old Caucasian women was admitted for the evaluation of a right adrenal mass, measuring 4 cm. The patient was asymptomatic, never hypertensive. Standard endocrinological evaluation of the adrenal mass revealed significantly elevated plasma and urine normetanephrine (>2 fold upper normal range) and metanephrine levels (>10 fold upper normal range). Subsequent functional imaging with MIBG SPECT/CT confirmed catecholamine storage in the left adrenal mass. After pretreatment with phenoxybenzamine (causing hypotension) the mass was removed surgically and a pheochromcytoma confirmed histologically. Second case: A 59-year old Caucasian women with repetitive hypertensive crises for several years was screened for pheochromocytoma and significantly elevated plasma and urine normetanephrine levels (> 5 fold upper normal range) were observed. MRI demonstrated a small left adrenal mass of 2 cm. Although no relevant tracer uptake was observed on MIBG SPECT/CT, subsequent somatostatin receptor imaging with DOTA-TATE PET/CT suggested adrenal pheochromocytoma (Fig.). After pretreatment with doxazosine the mass was removed surgically and a pheochromocytoma confirmed histologically, blood pressure normalized after surgery. Third case: A 67 year old Asian woman was admitted for the evaluation of a large left adrenal mass measuring 7.5 cm. She had well controlled hypertension with dual antihypertensive medication and did not suffer from paroxysmal hypertensive crises. Plasma normetanephrine levels were substantially elevated (>20 fold upper normal range). MIBG SPECT/CT confirmed catecholamine storage in the adrenal mass that was partly necrotic. After pretreatment with doxazosine the mass was removed surgically, a largely necrotic pheochromocytoma was confirmed histologically. No further antihypertensive treatment was necessary. Conclusions: These cases demonstrate that a pheochromocytoma may be asymptomatic, any adrenal mass needs standard endocrinological workup. Standard functional imaging has a limited sensitivity, additional approaches have to be considered.