The use of endoscopic ultrasound (EUS) in ZES/MEN1 is controversial because it detects <50% of duodenal lesions but is the most sensitive modality for detecting pancreatic NETs or pancreatic gastrinomas (the latter occurring in <5–20%) [18,226,494,495,496]. The gene discussed is MEN1; the disease is pancreatic neuroendocrine tumor.