Melanoma is a cancer that originates in the pigment-producing cells of the skin (melanocytes).
Melanocytes are the pigmented cells in the skin that give skin its distinctive color. Sunlight stimulates melanocytes to produce more melanin (the pigment that darkens the skin) and increases the risk of melanoma.
Melanoma can begin as a new, small, pigmented skin growth on normal skin, most often on sun-exposed areas, or it may develop from preexisting pigmented moles (see Noncancerous Skin Growths: Moles). Sometimes melanoma runs in families. Melanoma readily spreads (metastasizes) to distant parts of the body, where it continues to grow and destroy tissue.
Melanomas can vary in appearance. Some are flat, irregular brown patches containing small black spots. Others are raised brown patches with red, white, black, or blue spots. Sometimes melanoma appears as a firm black or gray lump.
A new mole or changes in a mole—such as enlargement (especially with an irregular border), darkening, inflammation, spotty color changes, bleeding, broken skin, itching, and pain—are warnings of possible melanoma. If these or other findings lead doctors to suspect melanoma, they do a biopsy. They remove the entire growth if it is small or only part of it if it is large. The tissue is then examined under a microscope to determine whether the growth is a melanoma and, if so, whether all the cancer has been removed.
Most darkly pigmented growths that are sent for biopsy are not melanoma but, rather, simple moles. Nonetheless, removing a harmless mole is preferable to allowing a cancer to grow. Some growths are neither simple moles nor melanomas, but something in between. These growths, called atypical moles (dysplastic nevi), sometimes turn into melanoma later.
The less a melanoma has grown into the skin, the greater the chance that surgery will cure it. Almost 100% of the earliest, most shallow melanomas are cured by surgery. Thus, doctors treat melanomas by cutting them out, taking a border of almost ½ inch (1 centimeter) of skin around the tumor. However, melanomas that have grown deeper than about 1/32 inch (about 1 millimeter) into the skin have a greater chance to have spread (metastasized) through the lymphatic and blood vessels. Melanomas that have spread are often fatal.
Chemotherapy is used to treat melanomas that have spread, but few are cured. Some of the people treated live for less than 9 months. However, the course of the disease varies greatly and depends in part on the strength of the body's immune defenses. Some people survive in apparent good health for several years despite the spread of the melanoma. New and experimental treatments such as interleukin-2 and vaccines, which stimulate the body to attack the melanoma cells, have yielded promising results.
Because melanoma is often caused by long-term sun exposure, doctors recommend that people stay out of the sun and use protective clothing and sunscreen, starting in early childhood. However, doctors do not know how effective these measures are in preventing melanoma.
Anyone who has had a melanoma is at risk of developing other melanomas. Therefore, such people need yearly skin examinations. People who have many moles should have total body skin examinations at least once a year. In people without risk factors, doctors do not know whether routine yearly skin examinations reduce the number of deaths from melanoma.
Last full review/revision October 2008 by Gregory L. Wells, MD