Fig. 1. Contrast-enhanced abdominal pelvis computed tomography scan findings. (A, B) Axial and coronal images revealed a large polypoid mass in the duodenal bulb extending to the 2nd portion, measuring 4 cm in size.

Fig. 2. Esophagogastroduodenoscopy findings. (A) An 8-cm sized large duodenal polyp was noted at the bulb to 2nd portion of duodenum. The overlying mucosa exhibited a smooth surface. (B) The lesion was elevated following submucosal injection of a 5 mL mixture of epinephrine and hypertonic saline. (C) The snare was positioned on the base of the lesion. (D) Subsequently, the endoscopic mucosal polypectomy was performed using a snare. (E) Following the procedure, the exposed vessels at the base of mucosa were electrocauterized and three prophylactic hemoclips were applied. (F) The gross specimen was retrieved and measured.

Fig. 3. Histopathologic findings of the resected specimen. (A) The gross endoscopic resection specimen revealed a large duodenal lesion measuring 8 cm×2 cm×2 cm. (B) Massive hyperplasia of Brunner’s glands, mixed with smooth muscle, infiltrating inflammatory cells, and adipose tissue that represents Brunner’s gland hamartoma (hematoxylin & eosin stain, ×30). (C) Proliferated Brunner’s glands in lobules of various size (hematoxylin & eosin stain, ×150).