Subtypes and evolution

Junctional naevus — flat or barely elevated, evenly pigmented brown macule typically 2–6 mm. Nests of melanocytes at the dermoepidermal junction.
Compound naevus — slightly raised brown papule with pigmentation throughout. Nests at the junction and in the dermis.
Intradermal naevus — dome-shaped, skin-coloured to pale brown papule, often with overlying coarse hairs. Nests entirely within the dermis; junctional component lost.
- Miescher naevus — intradermal on the face, often pale.
- Unna naevus — intradermal on the trunk, often pedunculated.
Natural history — junctional → compound → intradermal over decades, ultimately involuting in older age.

Clinical features and demographics

Most adults of Northern European ancestry have 20–30 naevi; counts > 100 are an independent melanoma risk factor.
Peak count in the third decade, then gradual involution.
Distribution biased to sun-exposed body sites in Fitzpatrick I–III; truncal and lower-limb predominance reflects intermittent rather than chronic UV exposure.
Less common in Fitzpatrick IV–VI skin, but acral and mucosal naevi are proportionally commoner.
Pregnancy may darken existing naevi; this should not be assumed in any clinically atypical lesion.

Three benign global patterns dominate:
- Reticular — regular brown pigment network with thin lines and small uniform holes (commonest pattern in junctional naevi).
- Globular — uniform aggregated brown globules, often peripheral (compound naevi, young patients).
- Homogeneous structureless — uniform brown/blue area without network or globules (intradermal naevi).
Most acquired naevi are symmetric and show a single global pattern.
Multiple-component pattern, asymmetric pigment network, blue-white veil, atypical vessels or peripheral streaks/pseudopods should raise suspicion of melanoma.
"Ugly duckling" sign — a lesion that looks unlike the patient's other naevi — is more predictive than any single dermoscopic feature.

Individual naevi have a very low absolute risk of malignant transformation.
Total naevus count is the strongest patient-level predictor of melanoma — patients with > 100 naevi carry approximately a 7-fold relative risk.
Naevi > 5 mm and clinically atypical (dysplastic) naevi confer additional risk; see dysplastic naevus for the clinically atypical mole.
The naevus itself is rarely the site of transformation — most melanomas arise de novo. Naevus count is a marker of melanoma susceptibility, not a precursor inventory.

ABCDE — Asymmetry, Border irregularity, Colour variegation, Diameter > 6 mm, Evolution.
Ugly-duckling sign — a lesion that stands out from the rest of the patient's naevi.
Glasgow 7-point checklist or NICE NG12 weighted criteria — refer suspicious lesions on the urgent (2-week-wait) skin-cancer pathway.
Refer for suspected melanoma under the urgent skin-cancer pathway when any of: change in size/shape/colour, new pigmented lesion in an adult, persistent bleeding/itching/ulceration.
Biopsy any lesion with diagnostic uncertainty — narrow-margin (2 mm) excision biopsy is preferred for melanocytic lesions to preserve depth assessment.

Reassurance and education for typical benign naevi.
Excision indications — diagnostic uncertainty, repeated mechanical trauma, cosmetic preference, monitoring difficulty (hairline, intergluteal cleft, sole).
Avoid shave excision of pigmented lesions where melanoma is possible — depth assessment is essential.
Counselling — self-examination, photoprotection, sunbed avoidance, when to seek review.