Malignant melanoma involves cancerous changes to the skin cells that produce the skin's pigment, melanin. Melanoma may appear on normal skin or arise from a nevius (moles) or other lesion that has changed in appearance. Some congenital nevi may develop into melanomas. Spitz Nevi are benign lesions in children that do not develop into melanoma, but can be sometimes difficult to distinguish from melanoma.

There are 4 major types of melanoma:

• Superficial spreading melanoma is the most common type of melanoma, accouting for approximately 70% of cases. It is usually flat and irregular in shape and color with varying shades of black and brown. It may occur at any age or site and is most common in Caucasians.
• Nodular melanoma usually starts as a raised lesion that is dark black-blue or bluish-red, however some can lack color. Nodular melanomas account for approximately 15% of cases.
• Lentigo maligna melanoma occurs in about 5% of cases, usually in the elderly. It is most common in sun damaged skin on the face, neck, and arms. The lesions are usually large, flat, and tan with intermixed areas of brown.
• Acral lentiginous melanoma is the least common form of melanoma. It usually occurs on the palms, soles, or under the nails. It is more common in African Americans.

Melanoma is related to sun exposure, particularly to sunburns during childhood, and is most common in those with fair skin, blue eyes, and light hair.

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