RESUMO
Primary T-cell lymphoma of the duodenum is uncommon, and peripheral T-cell lymphoma of the duodenum is extremely rare. Approximately 90% of primary gastrointestinal lymphomas originate from B-cells and fewer than 10% originate from T-cells. A peripheral T-cell lymphoma involved in the small intestine is usually detected by complications such as gastrointestinal bleeding, perforation, or obstruction. A 57-year-old man complained of postprandial discomfort and weight loss of 5 kg for 1 month. An esophagogastroduodenoscopy showed a deep ulcer with blood clots and whitish exudates. We conducted a Whipple's operation because of the high risk of ulcer perforation and difficulty in distinguishing the ulcer from malignancy. The resected tissue was confirmed as a peripheral T-cell lymphoma. We reported a case of peripheral T-cell lymphoma of the duodenum and jejunum that extended to the pancreatic head where a diffuse lesion was found without any complications or specific symptoms.