Abstract
Few reports have presented data and results on functional (i.e., nuclear medicine) imaging of paragangliomas and pheochromocytomas (PGLs/PHEOs) for von Hippel–Lindau (VHL) patients. Nuclear medicine localization modalities for chromaffin tumors can be specific or nonspecific. Specific methods make use of the expression of the human norepinephrine transporter (hNET) and vesicular monoamine transporters (VMATs) by these tumors. These permit the use of radiolabeled ligands that enter the synthesis and storage pathway of catecholamines. Nonspecific methods are not related to the synthesis, uptake, or storage of catecholamines but make use of the tumors’ high glucose metabolism or expression of somatostatin receptors. Consensuses and guidelines suggest that metastatic and sporadic PHEOs/PGLs in VHL patients (as in patients with chromaffin tumors of yet unknown genotype) should be evaluated first with 18F-dihydroxyphenylalanine (18F-DOPA) positron emission tomography/computed tomography (PET/CT). The functional imaging of second choice is 123I-metaiodobenzylguanidine (123I-MIBG) for PHEOs in VHL patients. 123I-MIBG, 68Ga-DOTATATE/DOTATOC/DOTANOC PET/CT, or 18F-fluorodeoxyglucose (18F-FDG) PET/CT can be a second choice of functional imaging for PGLs in VHL patients.
Highlights
Pheochromocytomas and paragangliomas (PHEOs/PGLs; 70 and 30% of tumors, respectively) are rare chromaffin-cell neuroendocrine tumors represented by PGLs and PHEOs [1, 2]
In a study of 34 PHEO patients, 18F-DOPA positron emission tomography/computed tomography (PET/computed tomography (CT)) had equivocal results for adrenal uptake [36]. 18F- fluorodopamine (18F-FDA) positron emission tomography (PET) was superior to 123I-MIBG in the context of von Hippel–Lindau (VHL) syndrome: in 7/7 VHL patients, all their PHEOs were imaged with the former modality, whereas the latter was positive in 4/7 patients [37]
Since PHEOs/PGLs express to a high degree STRs type 2, 68 Gallium (68Ga)-DOTATATE PET/CT shows better diagnostic accuracy than “classic” SRS in the evaluation of PHEO patients; this can be attributed to the higher sensitivity of 68Ga-DOTATATE PET/CT [41]
Summary
Pheochromocytomas and paragangliomas (PHEOs/PGLs; 70 and 30% of tumors, respectively) are rare chromaffin-cell neuroendocrine tumors represented by PGLs (developed from paraganglia which can be localized from the base of the skull to the pelvic floor) and PHEOs (or adrenal paragangliomas) [1, 2]. PET with 18F-DOPA has been used for localizing PHEOs (sensitivity is reported at 89–97%) and is considered to be very accurate in imaging sporadic disease [19, 20]. 18F-FDG PET is a convenient and accessible modality for localizing PHEOs/PGLs that are negative with specific functional imaging modalities ( metastatic disease) (Figure 1) [22].
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