FFinalistSouthampton · 2027
Dermatology
AKT · Dermatology/Benign lesions

Melanocytic naevus

Benign proliferation of melanocytes (mole)

Overview

A benign proliferation of melanocytes (a "mole"). Junctional (flat, at the dermo-epidermal junction), compound (raised, both layers), and intradermal (dome-shaped, skin-coloured, older lesions). The whole point of the card is telling a benign naevus from melanoma using symmetry, uniformity and stability.

Recognise

  • Symmetrical, well-defined, uniform in colour, usually <6 mm and stable over time
  • Junctional = flat brown macule; compound = raised pigmented papule; intradermal = soft skin-coloured dome (often facial, older)
  • Most appear in childhood/early adulthood; numbers and atypia increase melanoma risk

Red flags

  • Change in size/shape/colour, asymmetry, irregular border, bleeding, or the "ugly duckling" lesion → excise to exclude melanoma

Differentials & how to tell them apart

Malignant melanomaasymmetry, border irregularity, colour variation, diameter >6 mm, evolution — a benign naevus is symmetrical, uniform and stable
Seborrhoeic keratosis"stuck-on" warty surface with horn cysts, not a smooth mole
Dermatofibromafirm dermal nodule with a positive dimple sign, not pigmented melanocytic
Pigmented BCCpearly with telangiectasia

Clinical image

We can't host this one — the image is DermNet's and their licence doesn't cover us republishing it. Their page for it is free to view.

Melanocytic naevus — clinical imagesDermNet

Investigations

Clinical ± dermoscopy. Excision biopsy of any lesion with ABCDE/ugly-duckling features (never just monitor a genuinely suspicious mole).

Management

Reassurance; excise (for histology) only if atypical or changing

  1. 1Reassure for typical, stable, symmetrical naevi; advise on sun protection and self-monitoring (ABCDE/ugly duckling).Gate: Excise rather than reassure if a mole is asymmetrical, has an irregular border, varied colour, is >6 mm or is CHANGING — and never shave-biopsy a lesion that could be melanoma (excise whole for Breslow thickness)
  2. 2Changing/atypical → excision biopsy for histology; numerous atypical naevi → surveillance ± dermatology.
Reassurance / no treatment — benign naevi need no intervention
Excision — for diagnostic doubt, repeated trauma, or cosmesis — send for histology

Key points

The exam tests the benign-vs-melanoma discrimination. An intradermal naevus on the face is a common, soft, skin-coloured benign dome — do not mistake the loss of pigment for sinister change.

Monitor & prognosis

Self-surveillance; review any change.

Benign; a minority of melanomas arise within a pre-existing naevus.

Source: NICE CKS Moles; DermNet