The unique characteristics of gastrinomas when detected in patients with MEN1 are well known and should be taken into consideration [47], the two main differences from sporadic gastrinomas being the pronounced multifocality of MEN1-related duodenal gastrinomas and the potential for synchronous pancreatic head gastrinomas and other functional- and non-functional PNEN, again complicating a possible surgical treatment. This evidence concerns the gene MEN1 and duodenal gastrin-producing neuroendocrine tumor.