and Paraganglioma by 18F-Fluorodeoxyglucose (18F-FDG) Positron Emission Tomography

Pheochromocytomas and paragangliomas (PPGLs) are rare catecholamine-producing tumors of the adrenal medulla and extra-adrenal sympathetic chromaffin tissues (1). Head and neck paragangliomas (HNPGLs) originate from vagal paraganglia. A large proportion of PPGLs and HNPGLs have a hereditary basis, often presenting as multiple tumors (2). These hereditary syndromes include multiple endocrine neoplasia type 2 (MEN2), von Hippel– Lindau (VHL) syndrome, neurofibromatosis type 1 (NF1), and paraganglioma syndromes associated with mutations of genes encoding subunits of the succinate dehydrogenase (SDH) complex, in particular subunits B (SDHB) and D (SDHD). SDHB mutations are associated with a particularly malignant phenotype (3,4). In patients with a biochemically established diagnosis of PPGL (5), anatomical and functional imaging are critical to localize the primary tumor, evaluate its multiplicity, and detect metastases, all of which guide the physician’s choice between curative surgery and palliative treatment. Computed tomography (CT) and magnetic resonance imaging (MRI) provide high sensitivity and allow precise delineation of the tumor. In most patients, anatomical imaging is complemented by functional imaging, which offers high specificity to positively identify the tumors as PPGL. The most widely used functional imaging technique is [123I]-metaiodobenzylguanidine single photon emission computed tomography (123I-MIBG SPECT). More recently, positron emission tomography (PET) has bee