Esophageal cancer is a disease that affects the esophagus, the long tube that connects the throat to the stomach. The chief symptom is difficulty swallowing (dysphagia), although this usually does not occur until the disease has advanced.

The esophagus is typically between 10 and 13 inches (25 and 32 centimeters) long and 3/4 inches (1.9 cm) wide at its smallest point. The walls of the esophagus are composed of specialized tissue layers, including:

• Mucosa. Inner lining of thin, flat cells (squamous or adenomatous).
  
  
• Submucosa. Layer below the inner lining containing mucus-secreting glands.
  
  
• Muscularis and advential layers. Rarely give rise to malignancy but are often invaded by esophageal cancers.
  
  
• Upper and lower esophageal sphincters. Thick bands of muscle tissue.

The esophagus plays an important role in swallowing and digestion. When a person eats or drinks, a muscle in the upper esophagus (known as the upper esophageal sphincter) relaxes. This movement allows food and liquid to enter the tube. The esophagus then closes to prevent food from backing up. A series of rhythmic contractions in the esophageal wall move the food down the tube. This process is called peristalsis, and it takes between four and 10 seconds.

The food continues to move down to the junction between the esophagus and the stomach, a ring of muscle known as the lower esophageal sphincter. This ring opens to allow food into the stomach and then quickly closes to prevent stomach acids and digestive enzymes from backing up into the esophagus

Cancer of the esophagus usually starts on the innermost layer before spreading outward to other layers. Eventually, it can grow large enough to create an obstruction that causes swallowing difficulties. It can also spread (metastasize) to surrounding tissues and organs.

Esophageal cancer is most dangerous after it has spread to nearby lymph nodes or other parts of the body. The most common sites for metastases include the lymph nodes, lungs, liver, brain, adrenal glands and bones. Survival rates for esophageal cancer remain low, but they are improving. Today, 17 percent of white patients and 12 percent of African-American patients live at least five years after being diagnosed with the disease, according to the American Cancer Society (ACS).

MOre than 15,500 new cases of esophageal cancer will be diagnosed in 2007, according to the ACS. The disease is three to four times more common in men than in women and about 50 percent more common in African-Americans than in whites. It is far more common in some countries than others. For example, rates of esophageal cancer are between 10 to 100 times higher in Iran, northern China, India and southern Africa than in the United States. 

In the United States, the ACS estimates that nearly 14,000 deaths will occur from esophageal cancer in 2007. Most people eventually die of this disease because it is usually detected after it has reached an advanced stage; however, survival rates are improving. The chances of survival typically increase if the cancer is detected in the earlier stages.