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Learn about moles (nevi), what causes them, whether they put you at increased risk of skin cancer and how to check a mole for signs of skin cancer.
Moles are a common type of skin growth. They often appear as small, dark brown spots and are caused by clusters of pigmented cells. Moles generally appear during childhood and adolescence. Most people have 10 to 40 moles, some of which may change in appearance or fade away over time.
Most moles are harmless. Rarely, they become cancerous. Monitoring moles and other pigmented patches is an important step in detecting skin cancer, especially malignant melanoma.
The typical mole is a brown spot. But moles come in different colors, shapes and sizes:
Moles can develop anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. Most people have 10 to 40 moles. Many of these develop by age 50. Moles may change in appearance or fade away over time. Hormonal changes of adolescence and pregnancy may cause moles to become darker and larger.
This ABCDE guide can help you determine if a mole or a spot may indicate melanoma or other skin cancers:
Cancerous (malignant) moles vary greatly in appearance. Some may show all of the features listed above. Others may have only one or two.
Make an appointment with your health care provider if a mole looks unusual, grows or changes.
Moles are caused when cells in the skin (melanocytes) grow in clusters or clumps. Melanocytes are distributed throughout your skin and produce melanin, the natural pigment that gives your skin its color.
Melanoma is the main complication of moles. Some people have a higher than average risk of their moles becoming cancerous and developing into melanoma. Factors that increase your risk of melanoma include:
The following measures can help limit the development of moles and the main complication of moles — melanoma.
Become familiar with the location and pattern of your moles. Regularly examine your skin to look for changes that may signal melanoma. Do self-exams once a month, especially if you have a family history of melanoma. With the help of mirrors, do a head-to-toe check, including your scalp, palms and fingernails, armpits, chest, legs, and your feet, including the soles and the spaces between the toes. Also check your genital area and between your buttocks.
Talk with your doctor about your risk factors for melanoma and whether you need a professional skin exam on a routine basis.
Take measures to protect your skin from ultraviolet (UV) radiation, such as from the sun or tanning beds. UV radiation has been linked to increased melanoma risk. And children who haven't been protected from sun exposure tend to develop more moles.
This article is written by Mayo Clinic Staff. Find more health and medical information on mayoclinic.org.
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