Moles are growths on the skin. Doctors call moles nevi (one mole is a nevus). These growths occur when cells in the skin, called melanocytes, grow in a cluster with tissue surrounding them. Moles are usually pink, tan, brown, or flesh-colored. Melanocytes are also spread evenly throughout the skin and produce the pigment that gives skin its natural color. When skin is exposed to the sun, melanocytes produce more pigment, causing the skin to tan, or darken.

Moles are very common. Most people have between 10 and 40 moles. A person may develop new moles from time to time, usually until about age 40. Moles can be flat or raised. They are usually round or oval and no larger than a pencil eraser. Many moles begin as a small, flat spot and slowly become larger in diameter and raised. Over many years, they may flatten again, become flesh-colored, and go away.

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