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Melanoma is a skin cancer that begins 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 76,000 people are diagnosed with melanoma and about 10,000 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 of melanoma.
Melanoma usually begins on normal skin as a new, small, pigmented growth, most often on sun-exposed areas. About one in three melanomas develops in a preexisting mole. Melanoma may also occur around and inside the eyes, in the mouth, on the genitals and rectal areas, in the brain, and in the nail beds.
Melanoma readily spreads (metastasizes) to distant parts of the body, where it continues to grow and destroy tissue.
Risk factors for melanoma include the following:
Sun exposure (mainly repeated blistering sunburns)
Repeated tanning with ultraviolet A (UVA) or psoralen plus ultraviolet A (PUVA) treatments
Skin cancer (another melanoma or another type of skin cancer)
Family members with melanoma or many atypical moles
Fair skin, freckling
Large numbers of atypical or pigmented moles
A weakened immune system
People who have had melanoma are at increased risk of developing a new melanoma.
Melanoma is less common among people who have darker skin. When melanoma does develop in darker-skinned people, it often develops in the nail beds and on the palms and soles.
Although melanomas occur during pregnancy, pregnancy does not increase the likelihood that a mole will become a melanoma. Moles frequently change in size and darken during pregnancy. Pregnant women should know the ABCDEs of melanoma so they can check their moles for any malignant (cancerous) changes.
A new mole or changes in a mole—such as enlargement (especially with an irregular border), darkening, inflammation, spotty color changes, bleeding, skin covering the tumor is broken (ulceration), itching, tenderness, and pain—are warning signs of possible melanoma and so are the ABCDEs of melanoma. If these or other findings lead doctors to suspect melanoma, they do a biopsy. For the biopsy, doctors remove the entire growth if it is small or only part of it if it is large and then examine the sample 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 removed 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. There are additional tools that doctors may use to help distinguish an atypical mole from a melanoma. These include polarized light and dermoscopy which help to better evaluate the lesions.
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, people can help prevent this cancer by doing the following, starting in early childhood:
Avoiding the sun: For example, seeking shade, minimizing outdoor activities between 10 am and 4 pm (when the sun’s rays are strongest), and avoiding sunbathing and the use of tanning beds (particularly adolescents and young adults)
Wearing protective clothing: For example, long-sleeved shirts, pants, and broad-brimmed hats
Using sunscreen: At least sun protection factor (SPF) 30 with UVA and UVB protection used as directed and reapplied every 2 hours and after swimming or sweating but not used to prolong sun exposure
However, doctors do not have enough evidence to know for sure whether these measures reduce the chances of people developing or dying of melanoma. However, these measures do decrease the risk of developing certain other skin cancers (basal cell carcinoma or squamous cell carcinoma).
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. 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), taking a border of almost ½ inch (1 centimeter) or more 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 to (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.
The new immunotherapy drugs pembrolizumab and nivolumab are used to help the body's immune system destroy the cancer. These drugs are called PD-1 inhibitors because they block the action of a protein on the surface of the cancer cell called programmed cell death protein 1. This protein protects the cancer cell from the effects of the immune system. When PD-1 inhibitors block the protein, the immune system is able to attack the cancer cell and kill it. PD-1 inhibitors are proving to be very effective treatments for metastatic melanoma. Ipilimumab is another immunotherapy drug that helps activate certain white blood cells to attack cancer cells and improves survival.
Other newer drugs that can improve survival in melanoma that has spread include dabrafenib and vemurafenib. 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 (called targeted therapy).
Radiation therapy may be used in people whose cancer has spread to the brain.
Other treatments are being investigated, such as other drugs and vaccines that stimulate the body to attack the melanoma cells.
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