Abstract
A 70-year-old woman was admitted because of epigastric pain. Upper gastrointestinal endoscopy did not reveal any tumor, however, abdominal CT showed swelling of a peripancreatic lymph node, and a diagnosis of neuroendocrine tumor was made by endoscopic ultrasound-guided fine needle aspiration biopsy. PET-CT showed intense accumulation in the duodenal wall. Pancreatoduodenectomy was performed for the preoperative diagnosis of duodenal neuroendocrine tumor with lymph node metastasis. The resected specimen only had a slightly convex lesion in the duodenum adjacent to the pylorus. However, pathological examination revealed a tumor measuring 20 mm in diameter, which infiltrated into the muscular layer, and a pathological diagnosis of duodenal neuroendocrine tumor was made. The tumor failed to be detected by upper gastrointestinal endoscopy, conceivably because it was in the blind spot. We encountered a rare case of duodenal neuroendocrine tumor, which scarcely appeared as an elevated lesion despite its large size.
