Differences between Malignant Melanoma and a Normal Mole

Melanoma is a form of skin cancer. It arises from specialized skin cells called melanocytes, which produce the color (pigment) in our skin. Melanomas are pigmented lesions that resemble normal skin moles. However, melanomas usually have characteristics that distinguish them from moles. Being aware of the differences between moles and melanomas enables you to monitor your skin for the possible development of melanoma. Five distinguishing characteristics to look for are represented by the mnemonic ABCDE where "A" is for asymmetry, "B" is for border irregularity, "C" is for color variegation, "D" is for diameter and "E" is for evolving.

A dermatologist looking at a patient's mole. (Image: Dean Bertoncelj/iStock/Getty Images)

Asymmetry

Normal moles—called nevi—are typically symmetrical, which means that if you were to draw a line down the middle of it, the two halves would look like mirror images of each other. Melanomas are most often asymmetrical. If you drew an imaginary line down the middle of a melanoma, the two sides would not look alike.

Border

The border or edge of a mole is generally smooth and distinct. It is clear where the mole ends and the regular skin begins. Melanomas typically have irregular borders that may have a blurry appearance. Melanomas may have a white ring or halo around them, which is an area of skin without any pigment surrounding the lesion. Melanomas may also have satellites, tiny areas of pigment that are beyond what appears to be the border of the lesion.

Color

A normal mole is usually a single color. In contrast, melanomas are typically more than one color. Shades of tan, brown and black are common in melanomas. Small areas of white, red and blue may also be present. Sudden darkening of a preexisting mole may be a sign that it has transformed into a melanoma.

Diameter

Most melanomas measure more than 6 millimeters across--about as big around as the diameter of a pencil. Although some melanomas are smaller than 6 millimeters and some moles are larger than 6 millimeters, using this cutoff can help determine if a lesion is suspicious.

Evolution

Evolution in this context refers to whether a lesion is changing. Moles generally do not change, or they change slowly over many years. In contrast, melanomas can change rather quickly. They may change in size, shape, color or other ways such as becoming ulcerated or beginning to itch.

Evolution also refers to a lesion that is unlike the others. If a spot on your skin looks like all your other moles, then it probably is just another mole. However, if the spot is different from your other moles in one or more ways, that could be a red flag for melanoma.

Surface Characteristics

Melanomas can have surface characteristics that moles usually do not have. These include scaliness, crusting, oozing, ulceration and bleeding.

Symptoms

Melanomas can cause symptoms that moles usually do not. A pigmented skin lesion that is painful, tender or itches is suggestive of a melanoma.

Melanoma is a potentially deadly cancer, which typically shows some or all of these ABCDE changes. Other times the changes can be subtle and difficult to appreciate. If you notice a suspicious spot on your skin, see your doctor to have it checked. Early detection is the key to survival with melanoma.

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