naevi

Naevi, or moles, are benign proliferations of melanocytes in the skin. They may be present at birth (congenital naevi) or develop later (acquired naevi). They range from flat to raised and from light tan to dark brown or black, and may be skin-colored.

Common acquired naevi include junctional, compound, and intradermal naevi. Junctional naevi are flat and located at the epidermal-dermal junction; compound naevi are raised and involve both the junction and the dermis; intradermal naevi are mainly in the dermis and are often skin-colored or lightly pigmented, sometimes with hair. Other types include blue naevi, which are deep dermal melanocytes producing a blue color, and dysplastic (atypical) naevi, which have irregular borders or color variation and may resemble melanoma; they occur in some individuals and can be associated with an increased risk of melanoma, especially if numerous or changing. Congenital naevi are present at birth; size varies, and large or giant congenital naevi carry a higher melanoma risk and may require regular surveillance or removal.

Most naevi arise from benign clonal proliferation of melanocytes. Genetic mutations (such as BRAF or NRAS) and sun exposure contribute to their development, with family history as a risk factor.

Clinically, naevi are usually diagnosed by examination. Dermoscopy can help characterize features. Any lesion showing asymmetry, border irregularity, color variation, diameter greater than about 6 mm, itching, or bleeding should be evaluated; biopsy or excision may be performed to exclude melanoma.

Management typically involves observation, sun protection, and patient education. Excision is considered for diagnostic uncertainty, cosmetic concerns, or changing lesions. The overall melanoma risk is higher with a greater number of naevi or with dysplastic naevi, but most naevi remain benign.