Helicobacter pylori (H. pylori) infection
H. pylori infection is a strong risk factor for certain types of stomach cancer. Ulcers. A peptic ulcer is a sore on the lining of your stomach, small intestine or esophagus. A peptic ulcer in the stomach is called a gastric ulcer. A duodenal ulcer is a peptic ulcer that develops in the first part of the small intestine (duodenum).