Monarch Disease Ontology entry MONDO_0003649 (esophageal neuroendocrine tumor) is a well differentiated, low or intermediate grade tumor with neuroendocrine differentiation that arises from the esophagus. Also known as: NEN of esophagus, NEN of oesophagus, esophageal NEN, esophageal NET, esophageal neuroendocrine neoplasm, esophageal well differentiated endocrine tumor, esophageal well differentiated endocrine tumor/carcinoma, esophageal well differentiated endocrine tumour.