Are Moles Dangerous?

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Almost everyone has moles and most of them are nothing to worry about. Certain moles, however, mean you have an increased risk of developing melanoma, the most serious form of skin cancer. It’s important to know which moles are harmless and which ones you and your doctor need to keep a close eye on. Melanoma develops in cells called melanocytes, which produce the melanin skin pigment and also form moles. When melanoma is caught early, it can be successfully treated, but if it spreads it can be deadly.

When Moles May Be a Sign of Danger

Most people have anywhere from 10 to 40 moles on their bodies. Common moles, which are not dangerous, are round, raised, no bigger than about a quarter inch in diameter, and may be pink, brown, black or blue. Moles represent an increased danger of developing melanoma when:

  • You have atypical moles, which are moles with irregular features, colors or shape.

  • You have more than 40 or 50 moles.

  • You notice any changes in a mole.

  • You have a mole that itches, bleeds, oozes or feels tender.

  • You were born with moles or developed them as an infant, especially large moles.

  • You have moles that developed after age 20.

A family history of melanoma is another indication of increased risk. In men, the most common location for melanoma is on the back. In women, melanoma is the most common form of cancer in women between 25 and 29, and is often found on the lower legs. Melanoma also appears commonly on the chest, head and neck. While melanoma only develops in the same kind of cells that form moles, it may appear as new spots on the skin rather than in existing moles. Only about 20 to 30% of melanomas develop in moles.

How to Check Your Moles for Danger Signs

Keep an eye on your moles by examining them monthly There’s an easy alphabetical guide you can bear in mind as you look for suspicious moles, called the ABCDE rule:

  • A, asymmetry: moles that are not round or have mismatched halves

  • B, border: moles with irregular borders

  • C, color: moles that have two or more colors

  • D, diameter:moles that are larger than 1/4 inch (about the size of a pencil eraser)

  • E, evolution:moles that have changed in any way, including size, color or shape. They may also become itchy or begin to bleed.

Melanoma can develop anywhere on the skin, so check for any new dark or pink spots as well as moles. Though sun damage raises the risk of melanoma, melanoma can also occur in places that don't get much sun, especially in people with darker skin or people of color. These include the bottoms of your feet, palms of your hands and under your nails.
The vast majority of moles are not dangerous, but because melanoma can be life threatening if it isn’t caught early, skin exams are important. In addition to your own monthly mole check, ask your dermatologist how often they’d like you to come in for a full body exam. If your doctor sees a suspicious mole, they usually recommend a biopsy—a tissue sample—that a lab will examine for signs of cancer. Most biopsies prove negative, but catching melanoma early increases the likelihood of successful treatment.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Jan 4
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