SKIN CANCER

DEFINITION

Skin cancer is a malignant growth on the outer layer of the skin. A malignant growth is one that has the potential to cause death. Skin cancers are often divided into two general groups: malignant melanomas and non-melanoma cancers.

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.

CAUSES

Heredity (the process by which genes are passed from one generation to another) is thought to be an important factor in the development of melanomas. For all forms of skin cancer, exposure to sunlight is probably the most important environmental factor. Research suggests that sunburns received early in one's childhood can lead to skin cancer later in life. A cancer usually does not show up until ten to twenty years after the sunburn has been received. For this reason, skin cancers seldom develop before a person reaches his or her twenties.

Other factors may also lead to skin cancer. For example, people who work with certain chemicals may be at risk for the disease. Also, people with weakened immune systems, such as those who have AIDS, may be more likely to develop some kinds of skin cancer.

SYMPTOMS

All forms of skin cancer develop according to a similar pattern. The first sign of a cancer is usually a change in the appearance of an existing mole, the presence of a new mole, or a change in the appearance of an area of the skin.

Basal cell cancer usually appears as a small lesion (wound) in the skin that lasts for at least three weeks. The lesion (pronounced LEE-zhun) looks flat and waxy, with shiny, rounded edges. There may be a sore at the center of the lesion that makes it look like a dimple. The lesion slowly grows larger if it is not treated.

A squamous cell cancer generally begins as a small raised bump on the skin. The bump may have a sore at its center. It usually does not itch or cause pain.

A common symptom of melanoma is a change in an existing mole. The mole may change color, size or shape. It may become tender or itchy. If it starts to bleed, the cancer may already have begun to progress.

Malignant melanoma is the least common type of skin cancer. It is also the most aggressive. It spreads to surrounding tissues very quickly. (Reproduced by permission of

Custom Medical Stock Photo

)

Specialists often recommend the ABCD rule in checking for melanomas. These letters come from the following steps:

• A symmetry. Moles are normally round. If a mole begins to take an unusual (asymmetric) shape, it may be cancerous.
• B order. A normal mole has a clear-cut border with the surrounding skin. A cancerous mole has an uneven border.
• C olor. Normal moles are tan or brown. A cancerous mole may be any mixture of red, white, blue, brown, purple, and/or black.
• D iameter. A normal mole is usually less than 5 millimeters (.25 inches) in diameter. Any mole that grows larger than that size may be cancerous.

DIAGNOSIS

Anyone who notices a suspicious-looking blemish on the skin should see a medical doctor. The doctor will ask about the history of the blemish, such as how long it has been there and whether it itches or bleeds, as well as other questions about the patient's health.

If a skin cancer is suspected, the doctor may take a biopsy of the blemish. A biopsy is a medical procedure in which a small sample of tissue is removed, usually with a thin needle. The tissue is then studied under a microscope. The presence of cancer cells can be detected with the microscope. The type of cancer present, if any, can be determined by the appearance of the cells.

It may also be necessary to determine how far the cancer has spread, if at all. Tests used to make this determination include X rays, blood tests, and various imaging tests. Imaging tests are tests used to study the composition and function of internal organs.

TREATMENT

The usual procedure for treating any form of skin cancer is surgery. The doctor cuts out the mole or diseased area of the skin with a scalpel. A small section of healthy tissue surrounding the cancer is also removed. The reason that healthy tissue is removed is to make sure that all cancer cells have been eliminated.

Other methods can be used to kill and/or remove a cancer also. For example, the cancer may be frozen with dry ice or liquid nitrogen. The dead tissue can then be easily removed. Radiation treatments are sometimes recommended for older people or in cases where surgery is not possible or desirable. Surgical removal of a cancer may be followed by cosmetic surgery to hide the scars left by cutting or freezing.

Basal cell cancer and squamous cell cancer are generally treated successfully by these methods. Advanced cases of melanoma may require more aggressive treatment. This is especially true if the cancer has begun to spread through the body. It may be necessary, for example, to remove a person's lymph nodes if they have become cancerous. Radiation therapy may also be recommended if the melanoma has spread to other parts of the body.

Alternative Treatment

There are no generally accepted alternative treatments for skin cancer. Some practitioners recommend therapies that may reduce one's risk for getting skin cancer. For example, they suggest a diet high in antioxidants, such as vitamins C and E. Antioxidants are chemicals that may slow down the growth of cancerous cells. Herbal remedies that may prevent skin cancer include natural antioxidants, such as bilberry, hawthorn, tumeric, and ginkgo.

PROGNOSIS

Both basal cell and squamous cell cancer are curable when treated promptly. The key to success is early detection and treatment of the conditions. The cure rate for both forms of cancer is nearly 100 percent.

Basal cell cancers are the most common type of skin cancer. They grow very slowly, making them easier to treat than melanomas. (© 1995

SPL

. Reproduced by permission of

Custom Medical Stock Photo

.)

The prognosis for melanoma depends on how far the disease has spread. If a melanoma is removed in its early stages, the cure rate may be as high as 95 percent. If the cancer has spread to other parts of the body, the cure rate drops dramatically. If it has reached the lymph nodes, for example, the survival rate after five years is about 50 percent. If the condition has gone beyond the lymph nodes, it may be considered incurable.

PREVENTION

Prevention is the best way to deal with all forms of skin cancer. The less one is exposed to sunlight, the less the risk of skin cancer. One way to avoid sunlight, of course, is simply to stay out of the sun. At the least, one should avoid the sun during the hottest part of the day, between 11 A.M. and 1 P.M When one is in the sun, he or she should use sunscreen with a protective factor of fifteen or more.

Regular self-examinations can also be helpful. A person should check once a month for unusual moles or other growths on the skin. If such growths are found, medical advice should be sought.

FOR MORE INFORMATION

Books

Kenet, Barney J., and Patricia Lawler-Kenet. Saving Your Skin: Prevention, Early Detection, and Treatment of Melanoma and Other Skin Cancers. New York: Four Walls Eight Windows, 1998.

Lane, William I., and Linda Comac. The Skin Cancer Answer. Garden City Park, NY: Avery Publishing Group, 1999.

Robins, Perry. Sun Sense: A Complete Guide to the Prevention, Early Detection and Treatment of Skin Cancer. New York: Skin Cancer Foundation, 1990.

Organizations

American Academy of Dermatology. 930 N. Meacham Road, Schaumburg, IL 60173. (847) 330–0230; (888) 462–DERM (3376).

American Cancer Society. 1599 Clifton Rd., NE, Atlanta, GA 30329. (800) ACS–2345. http://www.cancer.org

National Cancer Institute. 31 Center Drive, Bethesda, MD 20892–2580. (800) 4–CANCER. http://www.nci.nih.gov.

Skin Cancer Foundation. PO Box 561, New York, NY 10156. (800) 754–6490.

Web sites

"Ask NOAH About: Skin Cancer." NOAH: New York Online Access to Health. [Online] http://www.noah.cuny.edu/cancer/nci/cancernet/201228.html (accessed on October 31, 1999).

Cancer Care News. [Online] http://www.cancercarinc.org (accessed on November 4, 1999).