The most common precancerous lesion of esophageal cancer is Barret's esophagus, which is formed by the chronic stimulation of the esophageal epithelium by chronic reflux esophagitis. Of course, this includes some chronic esophageal ulcers and long-term leukoplakia of the esophagus. These recurrent esophageal ulcers could potentially transform into atypical hyperplasia and then further into carcinoma in situ. However, the progression from precancerous lesions to actual cancer can take a very long time, possibly many years or even over a decade. Therefore, having a precancerous lesion does not necessarily lead to esophageal cancer.