Uptake of 123I-metaiodobenzylguanidine by gastrointestinal stromal tumor

A 52-year-old woman was admitted with a large intraabdominal mass. 123I- metaiodobenzylguanidine (123I-MIBG) scintigraphy revealed considerable 123I-MIBG accumulation by the mass that was compatible with a diagnosis of paraganglioma. However, a spindle cell tumor that was identified using endoscopic ultrasound-guided fine needle aspiration before surgery was positive for CD117. The surgically resected mass was confirmed as a gastrointestinal stromal tumor (GIST). Although the mechanism of 123I-MIBG uptake by GIST has not been elucidated, GIST should be included in the differential diagnosis of intra-abdominal tumor with 123I-MIBG uptake.