4. b. Any mole with irregular borders should be checked out by a dermatologist.

"It’s one of the warning signs, so it’s worth getting checked out," said Martin Weinstock, MD, PhD, professor of dermatology at Brown University in Providence, R.I., and chair of the skin cancer advisory group for the American Cancer Society. He said that the ABCD early warning signs of melanoma are Asymmetry; irregular Borders; multiple Colors in the same lesion; a Diameter of greater than 6 mm (the size of a pencil eraser).