A naevus is a hamartoma of the skin (a benign over-growth of normal tissue). A melanocytic naevus is a proliferation of pigmented melanocytes.
Melanocytic naevi occurring only in the dermal– epidermal junction are referred to as junctional naevi.
Melanocytic naevi occurring only in the dermis are referred to as dermal naevi. Blue naevi are acquired naevi occurring in the mid dermis.
Melanocytic naevi in the dermal–epidermal junction and the dermis are referred to as compound naevi.
Almost all naevi are benign, but malignant change may occur with junctional naevi at greatest risk. There is a familial dysplastic naevus syndrome (autosomal dominant, gene on the short arm of chromosome 1).
All individuals have one or more benign naevi, they appear as small hyperpigmented flat or slightly raised areas of skin. Atypical features and those suggestive of malignancy are described later in section Malignant Melanoma.
Benign naevi do not require any treatment. If there is any diagnostic uncertainty an elliptical excision biopsy and histopathological evaluation should be performed.