Serum Chromogranin-A Assay in Differential Diagnosis of Incidentally Discovered Adrenal Masses

Abstract

Adrenal incidentalomas are defined as asymptomatic adrenal masses occasionally discovered during high-resolution imaging procedures such as computed tomography (CT) or magnetic resonance (MR). Pheochromocytoma, a potentially lethal chromaffin tumour, must be excluded before any invasive diagnostic procedures to avoid massive catecholamines release. Chromogranin A (CgA) is a member of the granin family contained in secretory vescicles of chromaffin adrenal cells. Consequently, serum CgA increases in patients affected by pheochromocytoma and other diseases of the chromaffin system. This study investigated the performance of serum CgA assay in diagnosis of pheochromocytoma among patients affected by adrenal incidentaloma. Additionally, we evaluated the role of the CgA assay in selection of patients for ¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy, a very accurate but high-cost and time-consuming imaging procedure. We enrolled 104 patients affected by adrenal incidentally discovered masses and 100 healthy blood donors as controls. Serum CgA was assayed by a specific immunoradiometric method (IRMA) and ¹²³I-MIBG scan was performed in all patients. A cytological or histological diagnosis was obtained in all cases. Circulating CgA assay was positive in 12 out of 12 patients with pheochromocytoma and negative in 92 out of 92 patients with non-chromaffin adrenal nodules. Serum levels of CgA clearly increased from blood donors and patients with non-chromaffin adrenal nodules to patients with pheochromocytoma (p<0.0001). All patients with negative CgA assay showed a negative ¹²³I-MIBG scan. Serum CgA assay is effective in evaluating the presence of chromaffin tumour among patients with adrenal incidentaloma. A negative serum CgA assay rules out successive ¹²³I-MIBG imaging.