Melanocytic Naevi In Skin Of Color: Images And Clinical Guide

Melanocytic naevi, commonly known as moles, are benign proliferations of melanocytes, the pigment-producing cells in the skin. In individuals with skin of colour—typically Fitzpatrick skin types IV–VI—these lesions often appear darker, more uniform, and may exhibit distinct clinical and dermoscopic features compared to those in lighter skin tones. This article presents authoritative images and detailed descriptions to aid dermatologists, healthcare providers, and patients in recognizing and managing melanocytic naevi in diverse skin types.

Introduction to Melanocytic Naevi

A

melanocytic naevus

is a common benign skin lesion resulting from the local proliferation of melanocytes. These can be congenital (present at birth) or acquired (developing later). In skin of colour, naevi tend to be more heavily pigmented, often black or dark brown, due to higher baseline melanin production. Most individuals have 20–50 naevi, influenced by genetics, sun exposure, and immune status. Unlike in fair skin, where naevi may fade, those in darker skin often persist and darken with age or sun exposure.

Key characteristics include:

• Uniform colour, typically black in dark skin.
• Round or oval shapes, flat or raised surfaces.
• Possible hypertrichosis (increased hair) in compound or intradermal types.

Clinical Features in Skin of Colour

In darker skin, melanocytic naevi present with intensified pigmentation, making them stand out against the background skin tone. Junctional naevi appear as flat, evenly coloured mid-to-dark brown or black macules. Compound naevi are raised brown bumps, often hairy with a warty surface. Intradermal naevi are paler raised bumps, sometimes skin-coloured or pink, but in skin of colour, they retain more pigment.

Congenital melanocytic naevi, which form early in gestation (5th–24th weeks), are larger and may cover extensive areas like a ‘garment naevus’ or include satellite lesions. They can itch due to reduced sebaceous and eccrine gland function, leading to dryness and fragility. Puberty often causes darkening, raising, and increased hairiness.

Type	Clinical Appearance in Skin of Colour	Common Locations
Junctional	Flat, uniform black/brown macule	Trunk, limbs
Compound	Raised, dark brown, hairy bump	Face, back
Intradermal	Raised, paler but pigmented dome	Face, scalp
Congenital	Multi-shaded patch, possible satellites	Extensive, e.g., garment-like

Images from clinical cases show these features vividly: a black junctional naevus on the arm of a patient with Fitzpatrick type V skin appears uniformly pigmented without irregularity, distinguishing it from melanoma. Another depicts a compound naevus on the cheek, raised with terminal hairs.

Dermoscopic Features

Dermoscopy is crucial for evaluating naevi in skin of colour, where clinical darkness can mimic malignancy. Benign naevi show

uniform pigment patterns

: homogenous blue-grey in blue naevi, regular globules in compound types, or network patterns in junctional ones.

• Single colour or symmetric patterns: Nearly always benign; darker in pigmented skin.
• Vascular patterns: Comma-like or hairpin vessels in dermal naevi, often obscured by pigment.
• Congenital patterns: Irregular globules, fibrillar structures, or ‘cobblestoning’.

In halo naevi, a white rim surrounds the central lesion, with dermoscopy revealing symmetric hypopigmentation and fading globules. Nail apparatus naevi show uniform longitudinal melanonychia bands. The ‘ugly duckling’ sign— a naevus differing from others—warrants biopsy, especially if asymmetric or multicomponent.

Types of Melanocytic Naevi

Junctional Melanocytic Naevi

These flat lesions feature melanocytes at the dermo-epidermal junction. In skin of colour, they are sharply demarcated black macules, uniform under dermoscopy with regular networks. Image: Uniform black naevus on thigh.

Compound Melanocytic Naevi

Nests at junction and dermis create raised, darker lesions. Often hairy; dermoscopy shows globules atop networks. Prevalent on sun-exposed areas.

Intradermal Melanocytic Naevi

Confined to dermis, these are dome-shaped, less pigmented but still brown in dark skin. Prominent comma vessels on dermoscopy.

Congenital Melanocytic Naevi

Present at birth, linked to genetic mutations (e.g., NRAS). Giant forms (>20cm) risk neurocutaneous melanosis. In skin of colour, satellites are hyperpigmented.

Special Types

• Spitz naevus: Pink/brown dome in youth; starburst pattern.
• Blue naevus: Steel-blue homogenous.
• Reed naevus: Dark spindle cells on limbs.
• Halo naevus: Fading with immune response.

Diagnosis and Differential

Diagnosis relies on history, exam, and dermoscopy. ABCDE rule (Asymmetry, Border irregularity, Colour variation, Diameter >6mm, Evolving) applies but adapt for skin of colour—uniform black is often benign. Biopsy for atypia. Differentials: melanoma (asymmetric), seborrhoeic keratosis, pigmented BCC.

Complications and Risks

Benign but psychological impact from visibility. Rare melanoma risk in giant congenital naevi (2–5%). Itch, ulceration in large lesions. Neurocutaneous melanosis in 15% of giant cases.

Management

Observation for typical naevi. Excision for symptomatic, changing, or cosmetic concerns. Laser for hypertrichosis. Sun protection vital.

Frequently Asked Questions (FAQs)

Q: Are melanocytic naevi in dark skin more likely to be cancerous?

A: No, most are benign. Uniform dark colour is typical; monitor for ABCDE changes.

Q: How do naevi differ in skin of colour vs. white skin?

A: Darker, more persistent pigmentation; single uniform colour common on dermoscopy.

Q: When should a naevus be biopsied?

A: If atypical (ugly duckling), changing, symptomatic, or high-risk patient.

Q: Can congenital naevi disappear?

A: Rarely; they often enlarge proportionally or darken at puberty.

Q: Is dermoscopy useful in skin of colour?

A: Yes, reveals patterns obscured clinically, confirming benignity.

This article synthesizes clinical insights for better naevus recognition in diverse populations, emphasizing images for visual learning.