Heterotopic pancreas is a relatively infrequent lesion most often found in the stomach. Four histologic types are recognized: total, canalicular, exocrine, and endocrine heterotopia. To our knowledge, only 2 cases of purely endocrine heterotopic pancreas have been reported in detail. We describe the case of a patient with gastric and duodenal ulcers and gastric endocrine heterotopia. The lack of mass formation, histomorphology, and immunohistochemical features simulating islets of Langerhans supported the diagnosis. We conclude that purely endocrine heterotopic pancreas is a very rare entity that, when present, can simulate a primary or metastatic neuroendocrine tumor. Adequate sampling of the specimen, histomorphologic pattern, and immunohistochemistry are important for the purpose of distinguishing between a neuroendocrine tumor and purely endocrine pancreatic heterotopia.