Moles are clusters of pigmented cells and are usually harmless when they remain stable, symmetrical, and unchanged.
To identify potentially harmful moles, dermatologists use the ABCDE rule: Asymmetry (uneven halves), Border (irregular or blurred edges), Color (multiple or unusual shades), Diameter (larger than 6mm), and Evolving (any changes over time). Any mole matching one or more of these criteria should be evaluated by a doctor without delay.