How Do I Know if a Mole Is Cancer?
The vast majority of moles are not dangerous. Moles that are more likely to be cancer are those that look different than other existing moles or those that first appear after age 30. If you notice changes in a mole's color, height, size, or shape, you should have a dermatologist (skin doctor) evaluate it. You also should have moles checked if they bleed, ooze, itch, or become tender or painful.
Source: http://www.webmd.com
