Melanoma is a type of skin cancer. Often, the first sign of melanoma is a change in the size, shape, color or feel of an existing mole, according to the National Cancer Institute. If you have any of these signs, see your health care provider:
Asymmetry: The shape of half of the mole doesn't match the other.
Border: The edges are often ragged, notched, blurred or irregular; the pigment may spread into the surrounding skin.
Color: The color is uneven. Shades of black, brown and tan may be present. Areas of white, gray, red, pink or blue also may be seen.
Diameter: The size of the mole changes, usually growing larger. Melanomas are usually larger than the eraser of a pencil (a quarter-inch).