The symptoms below that may indicate esophageal cancer can also be symptoms of other disorders, such as GERD, Barrett's esophagus, and hiatal hernia, so a thorough examination is needed to make an accurate diagnosis.
Difficulty swallowing / feeling like food is stuck
Difficulty swallowing (dysphagia) is the most common symptom of esophageal cancer. If the esophagus narrows because of the cancer, it is more difficult for food to pass through the esophagus on its way to the stomach. This usually begins with larger pieces of food, but can then worsen to the point that even thin liquids won't go down easily.
Pain when swallowing
Pain may occur when swallowing if the cancer is large enough to block the esophagus. The pain may be felt within a few moments after swallowing, when the food or liquids reach the tumor and can't pass. Pain may also occur if the cancer causes a lesion in the lining of the esophagus or if it invades surrounding tissues. The pain is often felt in the chest or in the back between the shoulder blades.
To help pass food through the esophagus, the body makes more saliva. As it becomes more difficult to swallow, the body produces more saliva to compensate.
Heartburn often occurs. It's a burning sensation in the chest and throat.
Unexplained weight loss
Losing weight when not trying, and there is no other reason / cause for the weight loss.
The need to frequently clear your throat, and experiencing a hoarse voice that can't be explained by any other condition or illness.
This can either be food or blood. You may vomit blood that has seeped from the tumor into your esophagus or stomach.
Black, tarry stools
Bleeding from the esophagus can show up as black, tarry stools (melena) as stomach acid turns black.
Lightdale, M.D., Charles J.. "Esophageal Cancer." Vol. 94, No. 1, 1999. The American Journal of Gastroenterology. http://www.acg.gi.org/physicians/guidelines/EsophagealCancer.pdf
"What You Need to Know About Cancer of the Esophagus - Symptoms" National Cancer Institute. http://www.cancer.gov/cancertopics/wyntk/esophagus/page4