Abstract.Esophageal adenocarcinoma has shown a significant increase in incidence in recent years. It is thought that the development of gastroesophageal reflux disease (GERD), followed by columnar-lined esophagus and the development of dysplasia, leads to invasive adenocarcinoma. The exact pathogenesis of this process, the diagnosis and differentiation of the metaplastic and dysplastic esophageal lesions have yet to be determined. The purpose of this immunohistochemical study was to investigate the expression of pro-tumorigenic enzyme platelet 12-lipoxygenase (p12LOX) using two new available antibodies in non-dysplastic and dysplastic Barrett's esophagus. The stem cell markers nestin, CD117 and CD44, were then evaluated. The comparative group included GERD carditis, gastric intestinal metaplasia and colorectal adenoma. The overexpression of p12LOX detected by two specific antibodies in the non-dysplastic and dysplastic Barrett's mucosa clearly demonstrated that this enzyme plays an important role in the development of esophageal adenocarcinoma.