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Causes
By Mayo Clinic staff
Melanin is a natural pigment that gives your skin its color. It's produced in cells called melanocytes, either in the top layer of the skin (epidermis) or the outer layers of the skin's second layer (dermis). Melanin is then transported to the surface cells of your skin. Normally, melanin is distributed evenly, but sometimes melanocytes grow together in a cluster, giving rise to moles.
Scientists don't know why moles develop or what purpose they serve, if any, although they do appear to be determined before birth. Most moles are harmless and don't require special care, but some people have unusual-looking moles, called dysplastic nevi, which are more likely to turn cancerous than ordinary moles are.
