The vast majority of skin cancers are basal and squamous cell. A lesion that won't heal, bleeds easily and is traumatized easily, says Wang, characterizes basal and squamous cell carcinomas. Melanoma is formed from the pigment cells of the skin. Sometimes a mole of many years changes in size, shape, color or elevation, or starts to bleed. A is for asymmetry.
B is for border.
You should have a nice, clean regular border around your mole. Both A and B are good characteristics to have. On the other hand, C is for color. Change in color is a major indicator of a potential problem. And D is for diameter.