Melanoma is a cancer that originates in the pigment-producing cells of the skin (melanocytes).
Melanocytes are the pigment-producing 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.
Each year in the United States, more than 75,000 people are diagnosed with melanoma and about 9,000 people die from it. Although melanoma accounts for less than 5% of all skin cancers diagnosed in the United States, it causes the most skin cancer deaths. Every hour, one person in the United States dies from melanoma.
Melanoma can begin as a new, small, pigmented skin growth on normal skin, most often on sun-exposed areas, or it may develop in preexisting moles (see Moles). Melanoma may also occur in and inside the eyes, in the mouth, on the genitals and rectal areas, and in the nail beds.
Risk factors for melanoma include the following:
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 red, 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 (ulceration), itching, tenderness, and pain—are warnings of possible melanoma and so are the ABCDEs of melanoma (see see Sidebar 2: The ABCDEs of 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. If the biopsy shows that the growth is a melanoma and the growth has not been completely removed, it is then completely removed.
Most darkly pigmented growths that are sent for biopsy are not melanoma but, rather, simple moles. Nonetheless, removing even many harmless moles is preferable to allowing a single 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.
Melanoma may spread rapidly and cause death within months of diagnosis. 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. However, melanomas that have grown deeper than about 1/32 inch (about 1 millimeter) into the skin have a higher risk of metastasizing to the lymph nodes and blood vessels. Once melanoma has metastasized to the lymph nodes, the 5-year survival rate ranges from 25 to 70% depending on the degree of ulceration and the number of affected nodes. Once melanoma has metastasized to distant parts of the body, the 5-year survival rate is about 10%. Some people 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.
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. People can be taught to examine themselves to detect changes in existing moles and to recognize features suggesting melanoma (see Sidebar 2: The ABCDEs of Melanoma). In people without risk factors, doctors do not know whether routine yearly skin examinations reduce the number of deaths from melanoma.
Doctors treat melanomas by cutting them out (sometimes using Mohs microscopically controlled surgery [see see Sidebar 1: Mohs Microscopically Controlled Surgery]), taking a border of almost ½ inch (1 centimeter) of skin around the tumor. For people who have the most shallow melanomas (that is, melanomas that have not invaded past the epidermis—called melanoma in situ) and who cannot have surgery (for example, because their health is too poor) or choose not toy (for example, because their melanomas are in cosmetically important areas), doctors may treat with imiquimod cream or may use extreme cold (cryosurgery) to destroy the melanomas.
If melanoma has spread to the lymph nodes, the affected lymph nodes may be surgically removed. Chemotherapy is used to treat melanomas that have spread, but cure may not be possible. Treatments that have been used include dacarbazine, temozolamide, aldesleukin, and interferon alfa. However, newer drugs, such as ipilimumab and vemurafenib, are being used more. These drugs can often target the actual cancer cells more accurately than older cancer chemotherapy drugs. They do so by identifying abnormal genes that occur only in the cancerous cells. Other treatments are being investigated, such as other drugs and vaccines that stimulate the body to attack the melanoma cells.
Last full review/revision July 2013 by Gregory L. Wells, MD