stomach . About 4% of stomach ulcers are caused by a malignant tumor, so multiple biopsies are needed to exclude cancer. Duodenal ulcers are generally benign . Contents 1 Classification 2 Signs and symptoms 2.1 Complications 3 Cause 3.1 Stress 4 Diagnosis 4.1 Macroscopic appearance 4.2 Microscopic appearance 4.3 Differential diagnosis