SDHB and pheochromocytoma: The sensitivity of iodine123-MIBG scintigraphy for detecting pheochromocytoma is approximately 90 % [22], and known factors responsible for false-negative results include extra-adrenal or small adrenal pheochromocytoma, succinate dehydrogenase subunit B (SDHB) gene mutations, drug interference, and extensive necrosis in the tumor [1, 9, 23, 24].