Definition of Melanoma:

Melanoma is the most dangerous type of skin cancer. It is the leading cause of death from skin disease.

It involves cells called melanocytes, which produce a skin pigment called melanin. Melanin is responsible for skin and hair color.

Melanoma can also involve the colored part of the eye. For information about that form of melanoma, see melanoma of the eye.

See also:

• Basal cell skin cancer
• Skin cancer
• Squamous cell skin cancer

Causes, incidence, and risk factors:

Melanoma can appear on normal skin, or it may begin as a mole or other area that has changed in appearance. Some moles that are present at birth may develop into melanomas.

There are four major types of melanoma:

• Superficial spreading melanoma is the most common type of melanoma. It is usually flat and irregular in shape and color, with different shades of black and brown. It may occur at any age or body site, and is most common in Caucasians.
• Nodular melanoma usually starts as a raised area that is dark blackish-blue or bluish-red. However, some do not have any color.
• Lentigo maligna melanoma usually occurs in the elderly. It is most common in sun-damaged skin on the face, neck, and arms. The abnormal skin areas are usually large, flat, and tan with areas of brown.
• Acral lentiginous melanoma is the least common form of melanoma. It usually occurs on the palms, soles, or under the nails and is more common in African Americans.

Rarely, melanomas appear in the mouth, iris of the eye, or retina at the back of the eye. They may be found during dental or eye examinations. Although very rare, melanoma can also develop in the vagina, esophagus, anus, urinary tract, and small intestine.

Melanoma can spread very rapidly. Although it is less common than other types of skin cancer, the rate of melanoma is steadily increasing. It is the leading cause of death from skin disease.

The risk of developing melanoma increases with age. However, the disease also frequently affects young, otherwise healthy people.

The development of melanoma is related to sun exposure or ultraviolet radiation, particularly among people with fair skin, blue or green eyes, and red or blond hair.

Risks for melanoma include the following:

• Living in sunny climates or at high altitudes
• Long-term exposure to high levels of strong sunlight, because of a job or other activities
• One or more blistering sunburns during childhood
• Use of tanning devices

Other risk factors include:

• Close relatives with a history of melanoma
• Exposure to chemicals that can cause cancer, such as arsenic, coal tar, and creosote
• Presence of certain types of moles (atypical dysplastic) or multiple birthmarks
• Weakened immune system due to AIDS, some leukemias, organ transplant, medications used to treat illnesses such as rheumatoid arthritis