Localization of an Adrenocorticotropin-Producing Pheochromocytoma Using 18F-Dihydroxyphenylalanine Positron Emission Tomography

Abstract

A 67-yr-old man was evaluated for a fulminating ACTHdependent Cushing’s syndrome. The pituitary magnetic resonance imaging scan was normal. Computed tomography revealed a 2-cm left adrenal mass. Somatostatin receptor scintigraphy with In-pentreotide showed no abnormal uptake, but 6-fluoro-[F]L-dihydroxyphenylalanine positron emission tomography showed uptake in the left adrenal mass, highly suggestive of pheochromocytoma (Fig. 1). Plasma-free fractioned metanephrine and urine total fractioned metanephrine (free plus conjugated) were elevated (416.2 ng/liter and 979 g per 24 h, reference values 13.8 – 65.0 and 64.1–301.8). The patient wascured by adrenalectomy (Fig. 2). Histology of the tumor revealed a pheochromocytoma and hyperplasia of the surrounding adrenal cortex. Hydrocortisonesubstitutionwasnecessary for 5 months after surgery; afterward physiological cortisol secretion was restored. Despite extensive evaluation, including computed tomography, magnetic resonance imaging, and somatostatin receptor scintigraphy, in 12–19% of patients with ectopic ACTH