Cancer is a group of many related diseases. All cancers begin in cells
, the body's basic unit of life. Cells make up tissues, and tissues make up the organs of the body.
Normally, cells grow and divide to form new cells as the body needs them. When cells grow old and die, new cells take their place. Sometimes this orderly process goes wrong. New cells form when the body does not need them, and old cells do not die when they should. These extra cells can form a mass of tissue called a growth or tumor
Tumors can be benign or malignant.
Benign tumors are not cancer.
Usually, doctors can remove them. Cells from benign tumors do not spread to other parts of the body. In most cases, benign tumors do not come back after they are removed. Most important, benign tumors are rarely a threat to life.
Malignant tumors are cancer.
They are generally more serious. Cancer cells can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. That is how cancer cells spread from the original (primary
) tumor to form new tumors in other organs. The spread of cancer is called metastasis
The esophagus is the hollow, muscular tube that moves food and liquid from the throat to the stomach. The wall of the esophagus is made up of several layers of tissue, including mucous membrane, muscle, and connective tissue. Esophageal cancer starts at the inside lining of the esophagus and spreads outward through the other layers as it grows.
The wall of the esophagus has several layers:
- This is the layer that lines the inside of the esophagus and is comprised of three parts:
The epithelium forms the innermost lining of the esophagus and is 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.
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 contains glands that secrete mucus.
This is a thick band of muscle under the submucosa. This layer of muscle contracts in a coordinated, rhythmic way to push food along the esophagus from the throat to the stomach.
This is the outermost layer of the esophagus, which is formed by connective tissue.
Esophageal cancer starts in the inner layer (the mucosa
) and grows outward (through the submucosa
and the muscle layer). Since two types of cells can line the esophagus, there are two main types of esophageal cancer: squamous cell carcinoma
The esophagus is normally lined with squamous cells. The cancer starting in these cells is called squamous cell carcinoma
. This type of cancer can occur anywhere along the esophagus. Cancers that start in gland cells are called adenocarcinomas. This type of cell is not normally part of the inner lining of the esophagus. Before an adenocarcinoma can develop, gland cells must replace an area of squamous cells, which is what happens in Barrett's esophagus. This occurs mainly in the lower esophagus, which is the site of most adenocarcinomas.
Cancers that start at the area where the esophagus joins and the first two inches of the stomach behave and are treated like esophagus cancers, so are grouped with esophageal cancers.