Abstract
A 57-year-old female was referred to our department for treatment of a duodenal submucosal tumor (SMT), which had been growing over the last five years. Computed tomography demonstrated a marginally enhanced mass, measuring 36 mm in diameter, containing internal multiple hypovascular areas. Endoscopic ultrasonography-guided fine needle biopsy was performed using a 20-gauge core trap needle, and the specimens showed benign Brunner's glands. She underwent laparoscopic endoscopic cooperative surgery and the SMT was completely removed without any adverse events. Histology of the resected tumor showed Brunner's gland hyperplasia (BGH). BGH is generally a benign lesion. However, an accurate diagnosis is required to avoid overtreatment when it mimics malignancy.