Pheochromocytoma ; Brown adipose tissue ; Catecholamines ; Positron-emission tomography
Abstract
A pheochromocytoma is a tumor of chromaffin cells that originates from either the adrenal medulla or extra-adrenal
sympathetic tissues. The diagnosis of pheochromocytoma is based on elevated concentrations of plasma and urinary
catecholamines or their metabolites. In most patients, the anatomic localization of the tumor is determined with computed
tomography or magnetic resonance imaging. However, metaiodobenzylguanidine-scintigraphy or positron emission
tomography (PET) can also easily identify the foci of neuroendocrine tumors. We diagnosed a patient with pheochromocytoma
and high urinary norepinephrine levels, whose PET images revealed diffuse 18F-fluoro-2-deoxy-D-glucose (18FDG)
accumulation in the shoulder, lower neck, and perivertebral area. The regions of 18FDG uptake corresponded to the
location of human brown adipose tissue (BAT), which is minimally active in adults. It is thought that excessive
sympathetic stimulation by high circulating catecholamine concentrations augmented the metabolic activity and tracer
uptake in the BAT. This uptake in the BAT was normalized after surgical resection