Moles, also known as nevi, are a common kind of skin growth — most people have about 10 to 40 moles. They develop, usually in childhood or adolescence, when pigment cells (melanocytes) grow in clusters. Many people develop new moles over time, until about age 40. In older populations, moles tend to fade away. Common moles are about the size of a pencil eraser and are usually tan, brown or pink, but they also can be black, yellow, red, or blue. Most moles are round or oval, feel smooth or rough, and appear flat or raised.
Most common moles are harmless and require no treatment. It’s a good idea to be knowledgeable about the moles that you have and monitor their number, color, size, and shape. Any changes are usually harmless, although sometimes a change can herald skin cancer, especially malignant melanoma — the most serious form of skin cancer.
About 1 in 10 people have at least 1 unusual-looking mole — irregular shape, uneven color, or large size. These are known as dysplastic nevi and are more likely to develop into melanoma. Congenital nevi, or being born with large moles, can increase your risk of melanoma. New moles that appear over time — from childhood through adulthood, although rarely after age 40 — are known as acquired nevi. Congenital and acquired nevi rarely become cancerous. People who have more than 50 common moles, though, do have an increased risk of melanoma as do those with a family history of melanoma.
It’s best to familiarize yourself with the location, size, color, shape, and pattern of your moles through regular self-examination. A good rule to follow is the ABCDE rule, which describes the early signs of melanoma and other skin cancers: Asymmetry—one half of the mole does not match the other half; Border — the mole’s borders are uneven; Color — the mole has different colors or has changed colors; Diameter — the mole has increased in size; Evolving — the mole has changed in shape, color, size, or height or starts to itch or bleed. Some people, especially those with previous melanoma, may benefit from an annual skin exam by their doctor in addition to regular self-examination.
When should you worry about a mole? When should you consult your doctor? It’s best to let your doctor know about any mole changes or the appearance of new moles as soon as possible. Identifying cancerous skin growths early is integral to successful treatment. Most suspicious moles can be easily removed or biopsied for signs of cancerous cells. If melanoma is found, other treatments may be necessary, such as surgery to remove possibly sick lymph nodes, chemotherapy, radiation or biologic agents.
Prevention is also key to limiting the development of possibly cancerous moles. Using sunscreen year-round and avoiding the sun at peak times (usually between 10 a.m. and 4 p.m. in the mainland United States) can help protect your skin from the sun’s harmful ultraviolet (UV) radiation, which has been linked to increased risk of skin cancer. Broad-brimmed hats, long sleeves and pants, and sunglasses also can provide protection. And, of course, tanning beds should be avoided.
Here are some mole changes that you should be on the lookout for; if you notice any of these changes, it’s best to contact your doctor.
New moles may appear that are not completely symmetrical — one side of the mole doesn’t match the other side. Sometimes, an existing mole can become asymmetrical. If you notice an asymmetrical new mole or a change in symmetry in an existing mole, consult with your doctor.
Both an existing mole and new moles can have irregular borders---they can appear ragged, notched or blurred. The mole’s color can appear to spread into the surrounding skin. If irregular borders are an identifying feature of your mole, it’s best to contact your doctor.
Uneven Color or Multicolor
Common moles are usually a single color, usually tan or brown. But if an existing mole develops color changes, such as varying colors or shades of colors throughout the mole, it’s wise to have it checked out by your doctor. The same is true for a new mole---if the color is not consistent, let your doctor know.
Moles can sometimes increase in size, especially if it’s more than ¼ inch (about 6 millimeters) wide. Although melanomas can be tiny, most of them are larger than ¼ inch. Large congenital moles (larger than 2 inches) also should be watched. Likewise, if you notice a rapid change in mole size, action is necessary. Contact your doctor if you notice that one of your moles has changed in size or if a new large mole has appeared.
Changes Over Time
If you notice a change in a mole over time---either a few years or a few months, let your doctor know. These changes can take many forms, such as color, size, symmetry, or border. But there can be other changes to be on the lookout for as well. These include changes in the height of the mole or its texture (it becomes rough, dry, or scaly). Or the mole may become hard or lumpy or even start to itch, ooze or bleed. Any of these changes warrant a visit to your doctor.