MEN1 and Zollinger-Ellison syndrome: This will be somewhat complicated by the fact that liver metastases and gastrointestinal lymph node metastases in patients with long-standing MEN1/ZES can come from multiple sources (duodenal, pancreatic, gastric, thymic, lung) and a given patient can have simultaneous metastases from multiple sources [399], so these will have to be distinguished to establish the natural history of each primary source to allow therapy to be appropriately adjusted.