Merck Manual

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The ABCDEs of Melanoma

The ABCDEs of Melanoma

These warning signs are known as the ABCDEs of melanoma.

  • A—Asymmetry: Asymmetric (irregular) appearance (the two halves of the mole are not equal)

  • B—Borders: Irregular borders (that is, borders seem to blend in with the surrounding skin or are not round or oval)

  • C—Color: Changes in color of an existing mole, especially the spread of brown, black, red, white, or blue pigmentation or a color significantly different or darker than the person's other moles

  • D—Diameter: More than ¼ inch (about 6 millimeters) wide, about the size of most pencil erasers

  • E—Evolution: A new mole in a person over age 30 or a changing mole