False Positive Radioiodinated Metaiodobenzylguanidine (123I-MIBG)‎ Uptake in Undifferentiated Adrenal Malignant Tumor

Abstract EN

123I-Metaiodobenzylguanidine (123I-MIBG) scintigraphy is a widely used functional imaging tool with a high degree of sensitivity and specificity in diagnosis of pheochromocytoma.

However, rare cases of false positive reactions have been reported.

A 67-year-old male patient was admitted with epigastric pain.

Abdominal computed tomography (CT) revealed a heterogeneous left adrenal mass 6 cm in diameter; following hormone testing, 123I-MIBG scintigraphy was performed to determine the presence of pheochromocytoma, which confirmed eccentric uptake by a large left adrenal gland mass.

Chest CT and PET-CT confirmed metastatic lymphadenopathy; therefore, endobronchial ultrasound transbronchial needle aspiration was performed.

Metastatic carcinoma of unknown origin was suspected from a lymph node biopsy, and surgical resection was performed for definitive diagnosis and correction of excess hormonal secretion.

A final diagnosis of undifferentiated adrenal malignant tumor was rendered, instead of histologically malignant pheochromocytoma, despite the uptake of 123I-MIBG demonstrated by scintigraphy.