Advances in the diagnostic imaging of pheochromocytomas

Pheochromocytomas (PCs) and paragangliomas (PGLs) are routinely localized by computed tomography (CT), magnetic resonance imaging (MRI), and metaiodobenzylguanidine (MIBG) scintigraphy. CT can identify tumors with high sensitivity but rather low specificity. MRI has higher sensitivity and specificity than CT and is superior to detect extra-adrenal disease. Radioiodinated MIBG scintigraphy has been used for more than 30 years and is based on MIBG uptake via the norepinephrine transporter on the cell membrane. The technique is very useful for whole-body studies in case of multiple primary tumors or metastases. Tumors with sole production of dopamine usually cannot be visualized with MIBG and may require positron emission tomographic (PET) studies with 18F-labeled radiotracers. Somatostatin receptor scintigraphy (SRS) using the radiolabeled somatostatin analog octreotide (based on the expression of the somatostatin receptors 2 and 5 by the tumor) can demonstrate PGL or metastases not visualized by MIBG. In this article, we review the use of MIBG scintigraphy to diagnose PC/PGL and compare the sensitivity and specificity with that of CT and MRI. We also describe the recent SRS and PET techniques and review the latest results of clinical studies by comparing these imaging modalities. Future perspectives of functional imaging modalities for PC/PGL are finally presented.