Melanoma

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 Section 18, Chapter 215). 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.

See the sidebar Warning Signs of Melanoma.

Diagnosis, Treatment, and Prevention

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 a doctor to suspect melanoma, he performs a biopsy. Growths are usually removed entirely. 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, it is preferable to remove a harmless mole than to allow a cancer to grow. Some growths are neither simple moles nor melanomas but something in between. These tumors, called dysplastic nevi, or atypical moles, sometimes later turn into melanoma.

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 at least a ½-inch border of skin around the tumor. However, melanomas that have grown deeper than ¹/₃₂ inch into the skin are very likely 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 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 experimental treatments with interleukin-2 and vaccines that stimulate the body to attack the melanoma cells have yielded promising results.

Because melanoma is often caused by long-term sun exposure, people can help prevent this cancer by staying out of the sun and using protective clothing and sunscreen, starting in early childhood. Anyone who has had a melanoma is at risk of developing other melanomas. Therefore, such people need yearly skin examinations. People with a lot of moles should have total body skin examinations at least once a year.