Use the American Academy of Dermatology's "ABCDE" memory device to learn the warning signs that a spot on your skin may be melanoma: Asymmetry: One half does not match the other half. Border: The edges are not smooth. Color: The color is mottled and uneven, with shades of brown, black, gray, red or white. Diameter: The spot is greater than the tip of a pencil eraser (6.0 mm). Evolving: The spot is new or changing in size, shape or color