Skin Nevi

Pigmented nevi (moles) are growths on the skin that usually are flesh-colored, brown or black. Moles can appear anywhere on the skin, alone or in groups. Moles occur when cells in the skin grow in a cluster instead of being spread throughout the skin. Moles may darken after exposure to the sun, during the teen years and during pregnancy.​

In most cases, health care professionals can diagnose birthmarks based on the appearance of the skin. If a mole exhibits potentially cancerous changes, a biopsy may be performed​.