Duodenal masses range the full spectrum from benign to malignant. The pathologies within the duodenum are representative of the gastrointestinal tract. These unique entities can often present with variable symptoms, yet their most common presentations are related to obstruction, bleeding, and epigastric pain. The unique location of the duodenum allows for endoscopic assessment with diagnostic as well as therapeutic applications. Surgical resection remains the gold standard for treatment of many of these unique neoplastic processes. The reader will become familiar with several key benign and malignant entities of the duodenum.