There are two types of moles, typical and atypical. Both require monitoring, especially when there is a history of extreme sun exposure.
A typical mole, also called a nevus, is a non-cancerous (also known as benign) skin lesion that is made up of the color-producing cells of the skin. A mole that is present at birth is referred to as a congenital nevus. Typical moles enlarge evenly in all directions. After moles stop growing, they may persist or they may become smaller later in life. Sun exposure and heredity play a role in the development of moles. Moles may sometimes become warm or red in color or irritated by friction from rubbing or contact with rough clothing or by other types of injury.
Atypical moles, or dysplastic moles, are moles in which the cells grow in an abnormal way. Atypical moles may occur as new lesions or as a change in an existing mole. Lesions may be single or multiple. People with atypical moles may be at increased risk for developing skin cancer, with the risk increasing with the number of atypical moles present.