- Asymmetry. If you draw an imaginary line through the centre of a mole in any axis and both halves match then the mole is symmetrical and likely to be benign. (Asymmetry can be the first sign of melanoma).
- Border. Benign moles usually have an even, regular outline. Any indentations such as scalloped edges may indicate malignant change, such that one part of the mole is growing.
- Colour. Variation in colour may be a sign of dysplasia or malignant change in a mole. Melanomas may be intensely black and show variable colour within a single lesion from white to slate blue with all shades of black and brown. Amelanotic melanomas show little or no pigmentation.
- Diameter. Apart from congenital naevi, most benign moles are less than 1 cm in diameter. Any lesion growing to over 0.5 cm should be carefully checked. However, some melanomas are small - 0.1-0.2 cm.
- Evolving. A mole changing over time.
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