MEN1 and metastatic neoplasm: In this prospective study, 28% of ZES patients with advanced metastatic disease (unresectable liver or distant metastases), MEN1/ZES with imaged pancreatic tumors ≤1.5–2 cm, or an accompanying serious medical illness that limited life expectancy did not undergo routine surgical exploration [74,75,127,188], so the exact site of the primary tumor was not established surgically and the imaging studies were inclusive.