Characterization with hybrid imaging of cystic pheochromocytomas: correlation with pathology

Pheochromocytomas are rare neuroendocrine tumors derived from chromaffin cells arising from adrenal medulla, that may precipitate life-threatening hypertension or cardiac arrhythmias because of excessive catecholamine secretion (1). These tumors usually appear as solid hypervascular masses on imaging studies. Rarely, these lesions may undergo varying degrees of lesion degeneration such as cystic or intracellular lipid changes, or may be associated to the presence of necrosis, calcification and fibrosis, thus having unusual clinical as well as imaging appearances and thus mimicking other adrenal lesions (2). Of note, cystic lesions of the adrenal gland are uncommon, often asymptomatic and may also show malignant nature (3). Although cases of cystic pheochromocytoma have been previously reported (4), the diagnosis of these atypical pheochromocytomas is very challenging. We describe two cases of cystic pheochromocytomas with different clinical and morphologic features in which hybrid imaging using FDG PET/MRI or PET/CT reflected tumor characteristics; in particular, we highlighted the diagnostic pitfalls that can be encountered in imaging interpretation.