A mole is a skin growth made up of cells (melanocytes or nevus cells) that produce color (pigment). Moles can appear anywhere on the skin, alone or in groups.

Most moles appear during the first 20 years of a person's life. Some may not appear until later in life. Although most moles are harmless, some can become cancerous. Signs of skin cancer include a change in the skin, such as a growth, an irritation or sore that does not heal, or a change in a wart or mole.

• Moles are usually brown, but they can be blue, black, or flesh-colored.
• Size and shape may vary.
• During the teen years and pregnancy, moles tend to become darker and larger, and new ones may appear.
• Some moles may contain hairs, stay smooth, become raised or wrinkled, or fall off in old age.