Imaging characterization of benign and malignant pheochromocytoma or paraganglioma: comparison between MIBG uptake and MR signal intensity ratio

Abstract

In patients with pheochromocytoma or paraganglioma, iodine-131 MIBG uptake is able to differentiate between benign and malignant disease, while MR imaging is not useful for this purpose. The higher MIBG uptake observed in malignant lesions could reflect major tumor storage of catecholamines compared to benign lesions.

Advanced Adrenal Imaging: Comparison between Radionuclide and MR Techniques

“…In particular, storage catecholamine granules have been demonstrated within adrenal medullary tissue and Pheo tumour lesions [47]. Since MIBG uptake reflects the concentration of neurosecretory storage granules in chromaffin normal tissue and in the corresponding tumours, the higher MIBG uptake of lesions in patients with malignancies compared to those of patients with benign tumours, as we observed in our experience [49], suggests a higher concentration of catecholamine in malignant Pheo; thus, this difference could reflect different functional conditions with malignant lesions being more prone to catecholamine secretion crises compared to benign tumours. This observation might explain the severe hypertensive attacks that frequently occur in patients with malignant Pheo and might also justify the use of radiolabeled MIBG for therapeutic purposes in such patients when conventional treatments are not effective [52,53].…”

“…Lesions that concentrate MIBG can be benign or malignant and the ability of MIBG scan for tumour detection depends on both tumour size and differentiation [7,48]. Our results demonstrated that quantitative analysis of MIBG uptake may differentiate between benign and malignant Pheo, while MR imaging using signal intensity ratio measurement is not useful for this purpose; in fact, MIBG uptake, measured as tumour lesion OD IR, was significantly higher in malignant lesions compared to benign disease; this finding could depend on larger tumour size of malignant Pheo, but no significant difference in this parameter, measured on MR images, was found [49].…”

“…Previous comparative studies between MIBG and MR imaging demonstrated the complementary role of these techniques in the diagnostic evaluation of patients with Pheo or paraganglioma [19][20][21] however, in these studies no data regarding the characterization and differentiation between benign and malignant tumours have been reported. Recently, we demonstrated that in patients with Pheo MIBG uptake is able to differentiate between benign and malignant tumour lesions, while MR is not useful for this purpose [49] in particular, our results showed that there are no specific MR criteria, on both T1-and T2-weighted images, to differentiate between benign and malignant Pheo; in fact, no significant differences in MR signal intensity ratio were observed between tumour lesions of benign and malignant neoplasms; these results are likely due to the fact that MR signal intensity ratio reflects tumour tissue structural characteristics which are not related to metabolic and functional conditions; in this regard, when tumour dedifferentiation occurs in malignant lesions, MIBG fails to be concentrated and conversely tumour abnormalities become FDG avid [54]. Finally, a comparative study between CT, MR and C-11 MTO PET for the evaluation of adrenal incidentalomas has been reported showing that this radiocompound may be useful to characterize adrenal adenomas when CT and MR findings are uncertain [55].…”

Semiquantitative 123I-Metaiodobenzylguanidine Scintigraphy to Distinguish Pheochromocytoma and Paraganglioma from Physiologic Adrenal Uptake and Its Correlation with Genotype-Dependent Expression of Catecholamine Transporters

“…They demonstrated that the scoring system was highly specific and sensitive (91.5% and 100%, respectively) for detecting PPGL and is useful to discriminate normal adrenal 123 I-MIBG uptake from pheochromocytoma. Others have adopted this approach (19,23,33). However, a major disadvantage is that visual interpretation remains subjective and is highly observer-dependent.…”

“…Overall, specificities of 123 I-MIBG scintigraphy range between 70% and 100% for pheochromocytomas and 84% and 100% for paragangliomas, whereas sensitivities range between 85% and 88% and 56% and 76%, respectively (14)(15)(16)(17). Physiologic uptake of 123 I-MIBG by normal adrenal glands can give false-positive results or obscure small lesions (18)(19)(20). The sensitivity appears to be lower for extraadrenal, metastatic, recurrent, and certain hereditary PPGLs (14,16,(21)(22)(23)(24).…”