Intrinsic obstruction may be caused by Foreign body impactions Esophageal tumors (benign esophageal tumors or esophageal cancer) Esophageal rings Esophageal webs Strictures caused by gastroesophageal reflux or, rarely, caustic ingestion Extrinsic obstruction may be caused by compression resulting from An enlarged left atrium An aortic aneurysm An aberrant subclavian artery (termed dysphagia lusoria) A substernal thyroid gland Cervical bony exostosis A thoracic tumor For evaluation of potential esophageal obstruction, see Dysphagia.