Melanoma is a type of skin cancer that begins in melanocytes, cells in the outermost layer of the skin (epidermis) that make melanin—the pigment in skin. Besides giving skin its hue, melanin also protects other layers of the skin from the sun's harmful rays.
Skin cancer is the most common form of cancer, and while melanoma is less common than other types of skin cancer (such as basal cell and squamous cell carcinomas), it is more dangerous because it runs a higher risk of spreading to other parts of the body if left undetected and untreated.
Melanoma can develop anywhere on the skin, but there are a few common sites—such as the neck and face—where the sun has the most contact. In men, the chest and back are common sites. In women, melanoma often forms on the lower legs. Although it is primarily considered a skin cancer, melanoma can also form in the eyes, mouth, and vagina, but these are rarer than skin melanoma.
The National Cancer Institute estimates there will be more than 68,000 new cases of melanoma and nearly 8,800 melanoma-related deaths by the end of 2010.
Melanoma is one cancer where self-detection is possible. Once a month, look for changes in moles or freckles as well as sores that do not heal (use a mirror for hard-to-see parts of the body). Check moles for the "ABCD" of melanoma:
- Asymmetry—the shape of one half does not match the other half
- Border—the edges are irregular and ragged-looking,with notches or scallops
- Color—the color is unevenly distributed; besides black and brown, there may be blue, red, pink, white, or gray colors
- Diameter—melanomas are usually larger than 1/4 inch; also look for size changes in moles
One or more of the above features may be present in melanoma.
Risk factors for melanoma include:
- Skin tone—melanoma is more common in fair-skinned people
- Age—the risk of developing melanoma increases with age
- Ultraviolet light exposure (sunlight, sun lamps, and tanning booths)
- Moles—people with more then 50 moles have an increased risk of developing melanoma
- Gender—in the U.S., melanoma occurs more frequently in men than in women
- Weakened immune system
- Family history of melanoma—there is an increased risk of melanoma in people who have two or more close relatives with melanoma