<prompt> The most common site of carcinoma esophagus is:Upper 13 of esophagusMiddle 13 of esophagusLower 13 of esophagusGastroesophageal junction  <response>: The incidence of squamous cell esophageal cancer has decreased The rate of adenocarcinoma has risen dramatically. Adenocarcinomas arise in the distal esophagus in the presence of chronic gastric reflux and gastric metaplasia of the epithelium Barretts esophagus They behave clinically like gastric adenocarcinoma and account for 70 of esophageal cancers. Distribution: About 10 of esophageal cancers - upper third of the esophagus cervical esophagus 35 in the middle third 55 in the lower third. Ref: Harrison,E-18,P-764. 