Atypical moles are: Asymmetrical, with an uneven shape; have irregular Borders; are usually dark brown or black in Colour; have a Diameter the size of a pencil eraser (although it is best to find a melanoma before it has grown to this size); and are Evolving or changing. If any of your moles have these characteristics, see your doctor. Regular use of a broad-spectrum sunscreen (offering both UVA and UVB protection) has been proven to prevent premature skin aging and reduce your chances of developing skin cancer.