Melanoma is a kind of skin cancer. It isn't as common as other types of skin cancer, but it is the most serious.
Most melanomas show up as a new spot or skin growth. But they can also form in an existing mole or other mark on the skin. A melanoma usually looks like a flat mole with uneven edges and a shape that isn't the same on both sides. It may be black, brown, or more than one color.
Melanoma can affect your skin only, or it may spread to your organs and bones.