Melanoma is a disease in which malignant (cancer) cells form in the skin cells called melanocytes (cells that color the skin).
Melanocytes are found throughout the lower part of the epidermis. They make melanin, the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes make more pigment, causing the skin to tan, or darken.
Anatomy of the skin, showing the epidermis, dermis, and subcutaneous tissue. Melanocytes are in the layer of basal cells at the deepest part of the epidermis.
The skin is the body's largest organ. It protects against heat, sunlight, injury, and infection. The skin has 2 main layers: the epidermis (upper or outer layer) and the dermis (lower or inner layer).
When melanoma starts in the skin, the disease is called cutaneous melanoma. This PDQ summary is about cutaneous (skin) melanoma. Melanoma may also occur in the eye and is called intraocular or ocular melanoma. (See the PDQ summary on Intraocular (Eye) Melanoma Treatment for more information.)
There are 3 types of skin cancer:
- Basal cell skin cancer.
- Squamous cell skin cancer.
Melanoma is more aggressive than basal cell skin cancer or squamous cell skin cancer. (See the PDQ summary on Skin Cancer Treatment for more information on basal cell and squamous cell skin cancer.)
Melanoma can occur anywhere on the body.
In men, melanoma is often found on the trunk (the area from the shoulders to the hips) or the head and neck. In women, melanoma often develops on the arms and legs. Melanoma usually occurs in adults, but it is sometimes found in children and adolescents.
Unusual moles, exposure to sunlight, and health history can affect the risk of developing melanoma.
Anything that increases your risk of getting a disease is called a risk factor. Having a risk factor does not mean that you will get cancer; not having risk factors doesn't mean that you will not get cancer. People who think they may be at risk should discuss this with their doctor. Risk factors for melanoma include the following:
- Having a fair complexion, which includes the following:
- Fair skin that freckles and burns easily, does not tan, or tans poorly.
- Blue or green or other light-colored eyes.
- Red or blond hair.
- Being exposed to natural sunlight or artificial sunlight (such as from tanning beds) over long periods of time.
- Having a history of many blistering sunburns as a child.
- Having several large or many small moles.
- Having a family history of unusual moles (atypical nevussyndrome).
- Having a family or personal history of melanoma.
- Being white and male.
Possible signs of melanoma include a change in the appearance of a mole or pigmented area.
These and other symptoms may be caused by melanoma. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
- A mole that:
- changes in size, shape, or color.
- has irregular edges or borders.
- is more than 1 color.
- is asymmetrical (if the mole is divided in half, the 2 halves are different in size or shape).
- oozes, bleeds, or is ulcerated (a hole forms in the skin when the top layer of cells breaks down and the tissue below shows through).
- Change in pigmented (colored) skin.
- Satellite moles (new moles that grow near an existing mole).