Moles are small, usually dark, skin growths that develop from pigment-producing cells in the skin (melanocytes).
Moles vary in size from small dots to more than 1 inch (about 2.5 centimeters) in diameter but are usually less than 1 centimeter and tend to be less than 6 millimeters (about 1/4 inch). Almost everyone has a few moles, and many people have large numbers of them. Moles may be flat or raised, smooth or rough (wartlike), and may have hairs growing from them. Moles are typically flesh-colored, yellow, brown, blue-gray, or nearly black. They may be red at first but often darken.
Moles commonly develop in childhood or adolescence, and existing moles often enlarge (in proportion to the body's growth) and may darken. In some people, moles continue to develop throughout life. Moles can appear anywhere on the body. Moles respond to changes in hormone levels in women and may darken during pregnancy. Once formed, moles remain for a lifetime and get less pigmented and more raised or fleshy with time. In fair-skinned people, moles occur more commonly on sun-exposed areas of the skin.
Moles usually are easily recognized by their typical appearance. They are symmetric and have regular round or oval borders. They do not itch or hurt, and they are not a form of cancer. However, moles sometimes develop into or resemble melanoma, a cancerous growth of melanocytes (see see Melanoma). In fact, many melanomas begin in moles, so a mole that looks suspect should be removed and examined under a microscope (biopsy).
The following changes in a mole are warning signs of melanoma (known as the ABCDEs of melanoma):
People with more than 50 moles have a somewhat increased risk of melanoma. They should self-monitor for changes in their moles and also have them examined periodically as part of their primary care. If a mole becomes painful, itchy, bleeds, develops broken skin, or has any warning signs of melanoma, doctors may do a biopsy. If a mole proves to be cancerous, additional surgery may be needed to remove the skin surrounding it.
Most moles, however, are harmless and do not require removal. Depending on their appearance and location, some moles may even be considered beauty marks. Normal moles that are unattractive or located where clothing can irritate them can be removed by a doctor using a scalpel and a local anesthetic.
Atypical moles (dysplastic nevi):
Atypical moles tend to be multicolored, usually in tones of brown and tan with a pink background; asymmetric; and have irregular shapes and borders. They are often larger than (more than ¼ inch [about 6 millimeters] wide) most normal moles. Atypical moles most commonly appear on sun-exposed skin but may occur on covered areas (such as the buttocks, breasts, or scalp). The tendency to grow atypical moles may be hereditary. People with even a few atypical moles have an increased risk of developing melanoma.
People with atypical moles—particularly those with a personal or family history of melanoma—must look for any changes that might indicate melanoma. They may choose to have their skin checked at least yearly by a dermatologist to look for changes in the color or size of a mole. To help monitor such changes, dermatologists often use full-body color photographs. Some dermatologists closely inspect the skin using a hand-held instrument (a procedure called dermoscopy) to see structures in the mole that are not visible to the naked eye and that may indicate that melanoma is more or less likely. Atypical moles that change should be removed.
Skin damage caused by ultraviolet (UV) radiation from the sun is a cause of melanoma, particularly recreational sun exposure and sunburns. To limit damage caused by UV radiation, people should avoid the sun during peak hours (10 AM to 3 PM) when possible, wear sun-protective clothing, and use and frequently reapply a broad-spectrum sunscreen (such as one that protects against UVA and UVB radiation—see Sunscreens).
Last full review/revision June 2013 by Denise M Aaron, MD