Esophageal cancer is a malignant tumor of the esophagus (the muscular tube that propels food from the mouth to the stomach). Esophageal cancer occurs most often in men over 50 years old. There are two main types of esophageal cancer, distinguished by the way they look under the microscope: squamous cell carcinoma and adenocarcinoma. Squamous cell cancer is associated with smoking and alcohol consumption. The incidence of this disease in the United States has remained relatively constant, while the incidence of adenocarcinoma of the esophagus has risen dramatically.