A case of giant Brunner's gland hyperplasia of the duodenum diagnosed by endoscopic ultrasonography-guided fine needle biopsy.

A 60-year-old man was referred to our hospital due to upper abdominal pain and distension for 1 month. His past medical history was dilated cardiomyopathy. He had no significant abnormality on physical examination and blood tests were within normal range. Enhanced computed tomography (CT) demonstrated a marginally enhanced mass in the first portion of the duodenum, which was 40 mm in diameter and contained multiple small hypovascular areas. Esophagogastroduodenoscopy (EGD) revealed a large submucosal tumor (SMT) with a smooth surface in the bulbs of duodenum. The mass had no ulceration or no secretary orifice on the surface. Endoscopic ultrasonography-guided fine needle biopsy (EUS-FNB) revealed that the specimens were Brunner's glands hyperplasia (BGH). He underwent resection of the first portion of the duodenum and the pyloric part of the stomach. Pathologically, the resected mass showed giant BGH without any neoplasms. After surgery, his symptoms improved without any adverse events. This is a very rare case of giant SMT of the duodenum, which could be histologically diagnosed as BGH by performing EUS-FNB and was successfully treated by surgical resection. BGH is sometimes difficult to differentiate from neoplasia, when the size is large. EUS-FNB is useful for accurate diagnosis.