Moles are a common type of skin growth. They often appear as small, dark brown spots and are caused by clusters of pigmented cells. Moles generally appear during childhood and adolescence. Most people have 10 to 40 moles, some of which may change in appearance or fade away over time.when a mole that does not have the same color throughout or that has shades of tan, brown, black, blue, white, or red , it is suspicious and require further investigation.