Duodenal Brunner's gland hyperplasia is a relatively common duodenal elevated lesion, but there is currently no unified opinion on its diagnosis. Although there is little doubt about the diagnosis when the lesion presents with a typical appearance, it is often difficult to make a diagnosis in atypical cases. In this report, we describe a case of Brunner's gland hyperplasia, which was recognized by ultrasound endoscopy as a highly echogenic mass with multiple internal cystic components originating from the second and third layers, despite the atypical appearance of the mass.
