USEFULNESS OF 123I-METAIODOBENZYLGUANIDINE (MIBG) SCINTISCAN IN THE DIAGNOSIS OF JUXTA-ADRENAL SCHWANNOMA

The adrenal scintiscan with 123I-metaiodobenzylguanidine (MIBG), a rel iable morphofunctional technique to evaluate catecholamine turnover in adrenal tumors, can be a useful method to investigate adrenal inciden talomas with arterial hypertension. A male patient, 44 yr old with dia betes, unstable arterial hypertension, and sudden paroxysms of tachyca rdia 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-a drenal region, sized similarly to the neoplasm previously evidenced by CT scan. Histological findings of the surgically removed neoplasm wer e consistent with an ancient schwannoma. Apart from pheochromocytomas, the MIBG uptake is commonly reported in neuroblastomas. In neuroblast oma, a bidirectional process of transdifferentiation has been previous ly reported in vitro between two coexistent cells: cells with specific uptake system for norepinephrine, with 123I-MIBG uptake capability, a nd 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 conclusio n, the presence of adrenal tumors with MIBG uptake capability, apart f rom pheochromocytomas, neuroblastomas, ganglioneuroblastomas, and gang lioneuromas, must be considered in the diagnosis of adrenal tumors.