A woman in her 40s was was referred for evaluation of a 15-mm submucosal lesion in the transverse part of duodenum, which needed differential diagnosis of a gastrointestinal stromal tumor (GIST). Endoscopic ultrasound (EUS) revealed a 16-mm mass arising from the duodenal submucosa, showing an internal echo pattern similar to pancreatic parenchyma. EUS-guided Tissue Acquisition (EUS-TA) confirmed the mass as heterotopic pancreas, not GIST. Consequently, surgery was avoided, and the patient was conservatively followed. This case show efficacy of accurate preoperative diagnosis by EUS-TA for preventing unnecessary intervention.
