Skin Cancer - Description

The outer layer of the skin (the epidermis) contains three kinds of cells. Most of those cells are squamous cells. Cells near the bottom of the epidermis are called basal cells. And cells that provide pigment (color) to the skin are known as melanocytes (pronounced MELL-uh-no-sites).

Each type of cell can become cancerous. The three types of skin cancers, therefore, are squamous cell cancer, basal cell cancer, and malignant melanoma (cancer of the melanocytes). Malignant melanoma is by far the most serious form of skin cancer.

Other forms of skin cancer occur, but they are quite rare. The most serious of these is Kaposi's sarcoma (see Kaposi's sarcoma entry). At one time, Kaposi's sarcoma was very rare. It occurred primarily in older men of Mediterranean ancestry. It now occurs commonly in individuals with AIDS (see AIDS entry).

Exposure to sunlight is thought to be the major cause of skin cancers. About eight hundred thousand cases of squamous and basal cell cancers alone are diagnosed each year in the United States. The risk for skin cancers increases the closer one lives to the equator.

All forms of skin cancer begin with a single cell. For reasons that are usually not known, the cell begins to grow very rapidly. Its growth is soon out of control. It divides into two new cells, which continue growing wildly. Eventually the cancerous cells spread through a larger area. They can also begin to grow downward towards inner layers of the skin.

Malignant Melanoma

Malignant melanoma is the least common type of skin cancer. It is also the most aggressive. It spreads to surrounding tissues very quickly. It also invades other parts of the body, especially the lungs and liver.

Melanomas are probably caused by exposure to the sun. But they are also caused by genetic factors. A person is more likely to develop a melanoma if someone else in his or her family has also had the disorder.

Melanomas can occur anywhere on the body. Among Caucasians, they appear most often on the head, neck, arms, legs, and trunk of the body. Among African Americans, they occur primarily on the palms of the hands and the soles of the feet.

Basal Cell Cancer

Basal cell cancer is the most common form of skin cancer. It accounts for about 75 percent of all skin cancers. Light-skinned people are more likely to get the disease than are dark-skinned people. It usually appears after the age of thirty. Basal cell cancers grow very slowly, making them easier to treat than melanomas.

Squamous Cell Cancer

Squamous cell cancer is the second most common type of skin cancer. It grows more quickly than basal cell cancer, but less quickly than a melanoma. It can spread to other parts of the body, especially the lymph nodes. Lymph nodes are small round or oval bodies that are part of the body's immune system. Squamous cell cancer occurs most often on the arms, neck and head. This form of skin cancer is usually not life-threatening. But it can cause serious scarring.