A case of adrenal endothelial cyst (vascular type) with positive ¹²³I-MIBG uptake

¹²³I-metaiodobenzylguanidine (MIBG) scintigraphy is highly accurate for diagnosing pheochromocytoma and paraganglioma (PPGL), and positive uptake in non-PPGL adrenal lesions is rare. We report a 56-year-old woman with an adrenal endothelial cyst (vascular type) showing localized ¹²³I-MIBG uptake, initially suspected to be pheochromocytoma. After mild growth during observation, robot-assisted adrenalectomy was performed. Histopathology confirmed an endothelial cyst positive for CD31 and D2-40. Among 601 adrenalectomies, eight adrenal endothelial cysts (1.3 %) were identified, three showing MIBG uptake. Adrenal endothelial cysts may rarely show MIBG uptake, complicating preoperative differentiation from PPGL.