Your doctor can determine the type of mole you have by looking at it:
Common moles usually are no more than 1 to 10 millimeters (less than half an inch) in diameter. They are flesh-colored, yellow-brown or dark brown and can be located anywhere on the body. They usually appear during childhood or adolescence.
Atypical moles (dysplastic nevi) are usually larger in diameter (5 millimeters to 12 millimeters). They are tan to dark brown and may have a mixture of colors, including tan, dark brown, and sometimes pink or black. The border is often irregular and indistinct and often fades into the surrounding skin. Most commonly, atypical moles appear on sun-exposed skin, but they can occur elsewhere, and they continue to develop after age 35.