With the recommended, non-aggressive resections, most ZES/MEN1 patients with small tumors (<1.5–2 cm) and adequate acid secretory control have an excellent prognosis, which has led to controversy in their treatment, with many now managed non-surgically by a watch-and-wait approach [46,54,58,366,377,482,483,486,487]. This evidence concerns the gene MEN1 and Zollinger-Ellison syndrome.