Localization of pheochromocytoma and paraganglioma

If a pheochromocytoma is clinically suspected or diagnosed, the goal of imaging is lesion localization, and there are anatomical and functional imaging modalities used for it. CT is the anatomical modality of choice to identify an adrenal lesion or the less common extra-adrenal paragangliomas, and MIBG is the most widely used functional modality. Paragangliomas are frequently intra-abdominal (Blake et al. 24:S87–99, 2004), located in the retroperitoneum near the level of the SMA origin or aortic bifurcation (organ of Zuckerkandl) (Mayo-Smith et al. 21:995–1012, 2001). However, they may be encountered anywhere from the base of the skull to the urinary bladder, as they develop in the chromaffin tissue of the sympathetic nervous system (Blake et al. 24:S87–99, 2004), and other common extra-adrenal locations include the bladder wall, other parts of the retroperitoneum, heart, mediastinum, carotid body, and glomus jugulare body. MR is an alternate anatomical imaging localization modality; however, due to the greater availability, better spatial resolution and lower cost, CT remains the preferred initial anatomical imaging modality. The functional imaging modalities include nuclear medicine exams with a variety of radiotracers, including more specific tracers being developed as the biochemical characteristics of the tumors are better understood. Functional imaging has higher specificity and has great value as a confirmatory exam, and also to evaluate the possibility of multifocal lesions in abdominal and extra-abdominal locations, as well as metastatic lesions.