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These localised collections of melanocytes are extremely common and usually first appear during childhood. They increase during adolescence and may decrease in the elderly. Histological changes may occur during puberty and pregnancy. Most people have 5-20 melanocytic naevi. Many are acquired; some are inherited.
The importance of pigmented naevi lies in the identification of those with potential for malignant change - for example, include enlargement, altered pigmentation - increased or decreased - asymmetry, irregularity of the surface or edge, inflammation, bleeding, ulceration, itch or nodularity.
Individual melanocytic lesions may be clinically evaluated by (1):
Only photographic comparison helps in monitoring change in a particular lesion, which is important when observing for malignant transformation.
Excision is indicated if malignant transformation is suggested or for cosmetic reasons. However, less than 30% of melanomas arise from pre-existing naevi.