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Melanoma skin cancer sign: Diameter

A mole, showing its width compared to a pencil eraser

Melanoma is the most serious type of skin cancer. The most important warning sign of melanoma is a change in the size, shape, or colour of a mole or other skin growth, such as a birthmark.

  • A change in diameter (width) is one thing to watch for. Call your doctor if:
    • The width of a mole or skin growth is larger than 6 mm (1/4 inch), or about the size of a pencil eraser.
    • Any mole seems to be growing, even if it is still smaller than 6 mm (1/4 inch).

Current as of:
December 17, 2020

Author: Healthwise Staff
Medical Review:
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
Amy McMichael MD - Dermatology