GAST and Zollinger-Ellison syndrome: All patients with ZES, similarly to patients with other functional pancreatic neuroendocrine tumor (F-pNET) syndromes, have two major treatment problems—control of the functional syndrome due to the ectopically secreted hormone (i.e., gastrin) and treatment directed at the pNET itself, because in most F-pNET syndromes, except for insulinomas, the pNETs are malignant in >50% of cases [12,13,14,15,16,17].