Numerous studies report that MEN1/ZES patients not only can developed advanced stages of ECL cell proliferative changes (0–33%), but in contrast to sporadic ZES patients [25], they also frequently (10–30%) develop gastric carcinoids [61,62,77,116,159,161,165,166,177,184,191,192,193,194,195,196,197,198,199]. This evidence concerns the gene MEN1 and Zollinger-Ellison syndrome.