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How to Tell If Your Mole is Abnormal

Learning the Characteristics of Abnormal Moles

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Updated May 10, 2011

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Health experts recommend that we check our skin every month for signs of skin cancer and melanoma, but how do we know if a mole is normal or abnormal? Ultimately, a dermatologist is the only person who can differentiate between a normal and abnormal mole, but there are some ways to tell at home whether a mole may be abnormal. If you suspect that a mole may be abnormal, report it to your doctor as soon as possible.

The ABC Rule

The ABC's of skin cancer is a tool to help you identify abnormalities when examining your moles. Each letter represents an abnormal characteristic, including asymmetry, border, color, diameter, and evolution.

  • Asymmetry: Normal moles or freckles are completely symmetrical. If you were to draw a line through a normal spot, you would have two symmetrical halves. In cases of skin cancer, spots will not look the same on both sides.

  • Border: The borders or edges of an irregular mole are uneven, jagged or blurry.

  • Color: Normal moles are uniform in color. Moles are considered to be abnormal when they are more than one color or shade. This can include lightening or darkening of the mole.

  • Diameter: If a mole is larger than a pencil eraser (about 1/4 inch, or 6mm), it is considered to be abnormal. This includes moles that do not have any other abnormalities (color, border, asymmetry).

  • Evolving: Evolution refers to any changes in the symmetry, borders, colors, and diameter of an existing mole.

In summary, normal moles are typically small, have well-defined borders, are symmetrical, are brown and uniform in color, and are round.

If You Have An Abnormal Mole

First, don't panic. It is prudent that you have your mole checked out by your doctor or, preferably, a dermatologist. What you may think is abnormal may look completely normal to the trained eye of a medical professional. Second, you should know that not all abnormal moles are cancerous. Sun exposure is not the only cause for moles to become abnormal. Hormonal changes during puberty and pregnancy can cause benign skin changes, too.
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