If you draw a line through this mole, the two halves will not match.
The borders of an early melanoma tend to be uneven. The edges may be scalloped or notched.
Having a variety of colors is another warning signal. A number of different shades of brown, tan or black could appear. A melanoma may also become red, blue or some other color.
Diameter bigger than a pencil eraser
Melanomas usually are larger in diameter than the size of the eraser on your pencil (1/4 inch or 6 mm), but they may sometimes be smaller when first detected.
Any change — in size, shape, color, elevation, or another trait, or any new symptom such as bleeding, itching or crusting — points to danger.