Imaging of pheochromocytoma and paraganglioma

Abstract

Paragangliomas are tumours that arise within the sympathetic nervous system originating from the neural crest. These tumours can be found anywhere from the neck to the pelvis in locations of sympathetic ganglions. Although in the majority of paragangliomas the diagnosis is based on measuring catecholamines and metabolites in plasma or urine, imaging plays an important preoperative role. Today, there are several morphological and radionuclide imaging methods available that predict tumour localisation and tumour extent and give anatomic information to the surgeon. MRI is the morphological imaging modality of choice in localising pheochromocytomas and extra-adrenal paragangliomas. It provides excellent anatomic detail and has the advantage of lacking ionising radiation. The overall accuracy of computed tomography (CT) in detecting primary adrenal pheochromocytomas is very high, but CT lacks in specificity as difficulties may occur in distinguishing between paragangliomas and other tumour entities. The major advantages of radionuclide imaging are very high specificity and routinely performed whole-body scanning. Furthermore, metabolic imaging is not influenced by artifacts like scar tissue or metallic clips in post-surgical follow-up. Currently, a reported specificity of 99% and a cumulative sensitivity of about 90% in paragangliomas make (123)I-MIBG the most important nuclear imaging method. However, (18)F-DOPA-PET seems to be a very promising procedure which offers higher accuracy. The higher spatial resolution of PET-scanners enables the detection of small lesions not visualised with (123)I-MIBG. Both use of radiolabelled somatostatin analogue like (111)In-pentetreotide and (18)F-FDG is limited due to low specificity of the tracers and should be restricted to MIBG- and F-DOPA-negative cases.

18F-FDOPA PET and PET/CT Accurately Localize Pheochromocytomas

“…PET with 18 F-FDG, the main radiopharmaceutical imaging agent in oncology, has been shown to be limited because of the lack of specificity for neuroendocrine tumors (3,4), which are generally well differentiated and slow growing. 11 C-epinephrine and 11 C-hydroxyephedrine catecholamine analogs developed for studying the sympathetic nervous system have provided good results (4-6); however, their widespread clinical use is limited by the short physical halflife of 11 C, which limits the acquisition time and requires onsite cyclotron production.…”

Advances in the diagnostic imaging of pheochromocytomas

“…33,45,48 Significant uptake in the large intestine can be seen in late imaging in about 15% of the patients when 131 I-MIBG was used. 42,44 Uptake in bone tissue does not seem to occur. 44 Although MIBG was initially developed for visualization of the adrenal medulla, the normal adrenal medulla was rarely visualized with 131 I-MIBG, and a very faint adrenal uptake was reported in ,7% of the patients.…”

“…35 Normal uptake of MIBG is frequently seen in organs and tissues rich in sympathetic innervation, for example, the myocardium, lungs, spleen, liver, cerebellum, urinary bladder, colon, and salivary glands. [42][43][44][45][46][47] Uptake of 123 I-MIBG is found in the heart and lungs in about 90% of the patients. 33,45,48 Significant uptake in the large intestine can be seen in late imaging in about 15% of the patients when 131 I-MIBG was used.…”

Extra-adrenal Paraganglioma: An Uncommon Cause of Secondary Hypertension in a Young Subject

“…Plasma tests include measurements of catecholamines, metanephrines, and chromagranin A. False-positive elevations occur with stress, including venipuncture, medications (levodopa, labetalol, sympathomimetics). T2-weighted magnetic resonance imaging with gadolinium contrast is somewhat better than CT for imaging extra-adrenal pheochromocytomas and paragangliomas 8 . A heterogeneous, hypervascular, retroperitoneal mass with areas of necrosis with typical clinical setting is highly predictive of EAPs.…”