The Diagnostic Role of l-131 MIBG Imaging in Evaluation of Patients with Accidentally Discovered Asymptomatic Adrenal Masses

The aim of this study was to evaluate the role of I-131 MIBG imaging in the characterization of adrenal masses. Methods: A total of 23 patients (8 men, 15 women; mean age, 46±17 y) with accidentally discovered unilateral adrenal mass that had been originally detected on CT or MRI underwent I-131 MIBG adrenal scintigraphy. None of the patients showed specific symptoms of adrenal hypersecretion. Screening tests for excess cortical and medullary products showed normal adrenal hormone levels. Results: Histology after surgery was obtained. Adrenal lesions were represented: 13 had adenomas, 7 had nonadenoma benign lesions (4 pheochromocytomas, lcyst, 1 pseudotumor and I ganglioneuroma), and 3 had malignant tumors (2 carcinomas, and 1 metastases). Size range, 1.5- to 5-cm diameter; mean, 4.9±3.1 cm. For MIBG imaging, diagnostic sensitivity, specificity, and accuracy were 100%, 94%, and 96%, respectively; the PPV of the MIBG scan to characterize an adrenal mass as a medullary chromaffin tissue tumor was 83%, whereas the corresponding NPV to rule out this type of tumor was 100%. Conclusion: In patients with accidentally discovered adrenal masses, 1-131 MIBG adrenal imaging, may provide significant functional information for tissue characterization. MIBG scans is able to detect benign tumors such as pheochromocytoma, particularly when CT or MRI findings are inconclusive for lesion characterization.