[Contribution of nuclear medicine to the diagnosis of silent adrenal masses]

The role of adrenal scintigraphy in the noninvasive characterization of silent adrenal masses was investigated in 40 patients. The mass had been detected by US or CT performed in the evaluation of non-malignant extra-adrenal diseases (25 cases) or during staging or follow-up of a malignant extra-adrenal neoplasm (15 cases). In all cases radio-cholesterol scintigraphy (74 MBq i.v. of 131I-6 beta-iodomethylnorcholesterol in 19 cases; 11 MBq i.v. of 75Se-6 beta-selenomethylnorcholesterol in 21 cases) was performed; in 7 cases also 131I-MIBG scan (18.5-37 MBq i.v.) was carried out. When compared with CT data, radiocholesterol scintigraphy (standard or after suppression with dexamethasone) showed: concordant uptake (increased uptake of radiocholesterol on the side of the adrenal mass) in 24/26 patients with adrenal cortical adenoma; discordant uptake (absent or decreased uptake on the side of the adrenal mass) in 12 patients: 5 with adrenal metastases and 7 with non-adenomatous benign space-occupying lesions (2 ganglioneuromas, 1 post-traumatic hemorrhagic lesion, 3 adrenal cysts, 1 myelolipoma); indeterminate uptake (symmetric bilateral uptake) in 4 patients: 2 with a small adenoma, 1 with adrenal metastasis and 1 with a "false incidentaloma" (hepatic regenerative nodule). The results confirm the utility of radiocholesterol scintigraphy in demonstrating the benignity of adrenal lesions (particularly in identifying adrenocortical adenomas) and assess its place among the procedures used to characterize silent adrenal masses. The possible use of MIBG scintigraphy is also discussed.