Detailed Characteristic of Duodenal Gastrinoma Associated with Multiple Endocrine Neoplasia Type1 (MEN1) Detected by Esophagogastroduodenoscopy (EGD), Which was Buried under Ulcer

A 66-year-old Japanese male was shown to have severe ulcers with hypergastrinemia in the stomach through proximal horizontal part of the duodenum, who complained of dysphagia and vomiting. He suffered from gastric ulcer at 63, proven to have undergone parathyroidectomy for hyperparathyroidism at his 5th decade. Though had no definitely enlarged pituitary detectable by computed tomography (CT), he had slight defects in the visual field and hyperprolactinemia. A diagnosis of MEN1 was entertained. Follow up EGD revealed 5 small sessile submucosal tumors (SMTs) with a central depression or erosion in the duodenal bulb through descending part of the duodenum, which had been obscured beneath ulcers. Demonstrated in the regenerative mucosa by their biopsy were clusters of small tumor cells, which, though considered the tips of neuroendocrine (NE) tumor (NET) lying in the deeper layer, were not large enough to be proven so by immunostaining with the markers in the serial sections, and diffuse hyperplasia of synaptophysin-, chromogranin Aand gastrin-positive NE cells in Brunner glands (BGs), the preneoplastic lesion characteristic of MEN1-associated duodenal gastrinoma, supporting the diagnosis, which was firmly guaranteed by positively elevated glucagon-provoked plasma gastrin. Subtotal stomach-preserving pancreaticoduodenectomy (SSPPD) established the final diagnosis of duodenal gastrinomas graded G1 associated with MEN1, which were shown to be tightly contained in the densely conglomerated hyperplastic BGs. No metastases were detected. This is the first case in the world, in which all the three characteristics of MEN1-associated duodenal gastrinoma were demonstrated by EGD. Difficulty in endoscopically detecting the NET lies in the fact that, in addition to its smallness and deep localization, it might be buried under peptic ulcer at a certain stage of the natural history and that an attempt to biopsy it is hampered by the densely conglomerated barrier of the hyperplastic BGs in some cases.