Moles are colored, noncancerous skin growths. They can occur anywhere on the skin surface and virtually everyone has them. It is important to distinguish moles--also known as nevi--from the potentially life-threatening skin cancer melanoma. Melanomas are also colored skin growths, but they have characteristics that make them distinguishable from normal moles. In distinct contrast to melanomas, normal moles are uniform in color and shape with little to no growth over prolonged periods.
Most babies are born without moles. Moles begin to appear at about age 2 as junction nevi. These moles are flat or only slightly elevated above the skin surface. Color ranges from light brown to deep brownish-black. Junction nevi are typically less than 1/4 inch across and are usually hairless.
Compound nevi are slightly elevated moles that are round or oval, and they are either flesh-colored or a shade of brown. The surface may be smooth or irregular, much like a wart, and hair may be growing from the surface. These are small moles, typically less than 1/4 inch across. Compound nevi slowly become more elevated above the skin surface with increasing age. A variant of this type of mole is called a halo nevus, which is a compound nevus with a colorless area surrounding the mole.
Dermal nevi are more elevated above the skin surface than compound nevi. They are most commonly dome-shaped. A pedunculated form with a stalk-like base and a bulbous end often occurs on the neck, trunk or groin. Dermal nevi are brown to black, but the color often fades with advancing age. They vary in size from roughly the size of a peppercorn up to 1/2 inch across. The surface can be smooth, wrinkly or warty. Pedunculated dermal nevi may get caught on clothing or be scratched, causing bleeding.
Congenital nevi--also known as birthmarks--develop before birth and are present on a newborn. These nevi are flat and typically are brown or black, although pink or red variations occur. Birthmarks range in size from small spots to large lesions covering much of the face, trunk or extremities. They typically become thicker and elevate above the skin surface over time, occasionally developing a warty appearance. Large congenital nevi should be closely monitored because they can undergo cancerous transformation and become sites of melanoma, even in young children.
Nevus spilus is a flat to slightly raised brown spot dotted with smaller, brownish-black spots. This harmless mole is often oval, but the shape may be irregular. Nevus spilus is hairless and ranges in size from less than 1/2 inch to roughly 8 inches.
Blue nevi are round, slightly raised moles that typically arise in childhood. They contain a high concentration of brown pigment, but it is deep in the skin and causes the moles to have a dark-blue coloration. Blue nevi are typically less than 1/4 inch in size. They most commonly occur on the extremities.