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Cancer of the esophagus (also called esophageal cancer) starts when cells in the lining of the esophagus begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

To understand esophagus cancer, it helps to know about the normal structure and function of the esophagus.

The esophagus

The esophagus is a hollow, muscular tube that connects the throat to the stomach. It lies behind the trachea (windpipe) and in front of the spine. In adults, the esophagus is usually between 10 and 13 inches (25 to 33 centimeters [cm]) long and is about ? of an inch (2cm) across at its smallest point.

At the opening of the upper esophagus there is a special ring of muscle (called the upper esophageal sphincter) that relaxes to open the esophagus when it senses food or liquid coming toward it.

When you swallow, food and liquids travel through the inside of the esophagus (called the lumen) to reach the stomach.

The lower part of the esophagus that connects to the stomach is called the gastroesophageal (GE) junction. A special ring of muscle near the GE junction, called the lower esophageal sphincter, controls the movement of food from the esophagus into the stomach. Between meals, it closes to keep the stomach’s acid and digestive juices out of the esophagus.

Where esophageal cancer starts

Esophageal cancer can start anywhere along the esophagus. It starts in the inner layer of the esophagus wall (see below), and grows outward through the other layers.

The esophagus wall

The wall of the esophagus has several layers:

Mucosa: This layer lines the inside of the esophagus. It has 3 parts:

• The epithelium is the innermost lining of the esophagus and is normally made up of flat, thin cells called squamous cells. This is where most cancers of the esophagus start.
• The lamina propria is a thin layer of connective tissue right under the epithelium.
• The muscularis mucosa is a very thin layer of muscle under the lamina propria.

Submucosa: This is a layer of connective tissue just below the mucosa that contains blood vessels and nerves. In some parts of the esophagus, this layer also includes glands that secrete mucus.

Muscularis propria: This is a thick layer of muscle under the submucosa. It contracts in a coordinated way to push food down the esophagus from the throat to the stomach.

Adventitia: This is the outermost layer of the esophagus, and is formed by connective tissue.

Types of esophageal cancer

There are 2 main types of esophageal cancer, based on the type of cell it starts in.

Squamous cell carcinoma

The inner layer of the esophagus (the mucosa) is normally lined with squamous cells. Cancer starting in these cells is called squamous cell carcinoma. This type of cancer can occur anywhere along the esophagus, but is most common in the neck region (cervical esophagus) and in the upper two-thirds of the chest cavity (upper and middle thoracic esophagus). Squamous cell carcinoma used to be the most common type of esophageal cancer in the United States. This has changed over time, and now it makes up less than 30% of esophageal cancers in this country.

Adenocarcinoma

Cancers that start in gland cells (cells that make mucus) are called adenocarcinomas. Adenocarcinomas are often found in the lower third of the esophagus (lower thoracic esophagus). In some conditions, such as Barrett's esophagus, gland cells begin to replace the squamous cells in the lower part of the esophagus, and this might lead to adenocarcinoma.

Gastroesophageal (GE) junction tumors

Adenocarcinomas that start at the area where the esophagus joins the stomach (the GE junction, which includes about the first 2 inches (5 cm) of the stomach), tend to behave like cancers in the esophagus and are treated like them, as well.

Rare cancers in the esophagus

Other types of cancer can also start in the esophagus, including lymphomas, melanomas, and sarcomas. But these cancers are rare and are not discussed further here.