How to tell if moles are skin cancer

Written by kathleen blanchard, r.n.
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How to tell if moles are skin cancer
Malignant melanoma. (

A mole that has been present for a long time, or suddenly appears, may be skin cancer. Not all moles are cancerous, but existing moles can change character and become precancerous. There are several specific characteristics that may be signs of skin cancer. Follow the ABCD rule to determine if moles are skin cancer: asymmetry, borders, colour and diameter.

Skill level:


  1. 1

    Perform a regular examination of your skin for newly-formed moles, or changes in existing moles. Examine your skin in a mirror on a regular basis, front and back, and under your arms. Melanoma is a dangerous and invasive skin cancer that can appear anywhere on your body, even under your fingernails. Having a mole from birth increases the risk of melanoma. See a dermatologist if a new mole appears.

    Assymetry is a sign that a mole can be skin cancer. Look at each half of the mole, as if an imaginary line were drawn down the middle. If the mole is not even, have it examined.

  2. 2

    Inspect your moles for symmetry and a solid border. Borders that are not well defined may indicate skin cancer. Moles that itch, bleed or cause pain may also indicate skin cancer.

  3. 3

    Inspect the colour of your moles. Lack of uniform colour may be a sign of skin cancer.

  4. 4

    Inspect the diameter of your moles. Consistently check moles for increase in diameter. Moles or other skin lesions that are larger than a pencil eraser should be tested for skin cancer.

  5. 5

    See a doctor for testing. In order to determine if a mole is skin cancer, surgical excision of the borders of the mole is required. The tissue is then sent for evaluation by a pathologist.

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