Usefulness of 123I-metaiodobenzylguanidine (MIBG) scintiscan in the diagnosis of juxta-adrenal schwannoma.

The adrenal scintiscan with 123I-metaiodobenzylguanidine (MIBG), a reliable morphofunctional technique to evaluate catecholamine turnover in adrenal tumors, can be a useful method to investigate adrenal incidentalomas with arterial hypertension. A male patient, 44 yr old with diabetes, unstable arterial hypertension, and sudden paroxysms of tachycardia is described. The presence of a disomogeneous right juxta-adrenal neoplasm with calcifications was evidenced with ultrasound tomography and confirmed by computerized tomography (CT) scan. Adrenal 123I-MIBG scintiscan revealed a unilateral uptake at level of the right juxta-adrenal region, sized similarly to the neoplasm previously evidence by CT scan. Histological findings of the surgically removed neoplasm were consistent with an ancient schwannoma. Apart from pheochromocytomas, the MIBG uptake is commonly reported in neuroblastomas. In neuroblastoma, a bidirectional process of transdifferentiation has been previously reported in vitro between two coexistent cells: cells with specific uptake system for norepinephrine, with 123I-MIBG uptake capability, and cells oriented toward schwann/melanocytic line. The evidence of in vivo MIBG uptake in our schwannoma may be caused by the same possible phenotypic interconversion of above mentioned cell types. In conclusion, the presence of adrenal tumors with MIBG uptake capability, apart from pheochromocytomas, neuroblastomas, ganglioneuroblastomas, and ganglioneuromas, must be considered in the diagnosis of adrenal tumors.