Health A-Z

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Melanoma is usually visible as a single dark skin spot. It may appear anywhere on the body, but it most commonly develops on the back, chest, and legs. Most of the time, melanoma develops on normal-looking skin, but it can grow out of an existing mole.

Watch a mole for the A, B, C, D and Es of melanoma:

  • Asymmetry (one side doesn't match the other)

  • Border irregularities

  • Colors or shades of skin that are different within the same mole

  • Diameter larger than 6 millimeters (larger than a pencil eraser)

  • Evolving (a newly developing mole)

A mole that bleeds, feels numb, or has a crusty surface may also hint at melanoma.

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From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.

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