Brown spots on Mary's skin
The ABCD rule is:
* A is for ASYMMETRY: One-half of a mole or birthmark does not match the other.
* B is for BORDER: The edges are irregular, ragged, notched, or blurred.
* C is for COLOR The color is not the same all over, but may have differing shades of brown or black, sometimes with patches of red, white, or blue.
* D is for DIAMETER: The area is larger than 6 millimeters (about ¼ inch -- the size of a pencil eraser) or is growing larger.
…
