Melanocytic naevi: new classification

Why have a new classification?

A new classification system for melanocytic naevi has been proposed by Argenziano et al to account for dermoscopic features of these lesions.[1,2] Common use will tell whether the classification is useful, and no doubt it will evolve in time.

The conventional system has divided melanocytic naevi according to history (congenital or acquired) and histopathology (junctional, compound and dermal location of melanocytes). However clinical diagnosis is often imprecise. Historically, naevi were thought to start as junctional melanocytic nests, and progress to become compound then dermal in time. Careful dermoscopic observation of numerous naevi has shown this theory to be implausible.

Dermoscopy often allows precise diagnosis of different types of melanocytic naevi based on the amount and distribution of pigmentation. Often an individual has many benign naevi that look similar to one another, allowing the ugly duckling that looks different from the others to be recognised as a melanoma.

The new classification has seven groups. Clinicians may wish to use it when describing dermoscopic features of melanocytic naevi.

1. Globular (congenital) naevus
2. Reticular (acquired) naevus
3. Starburst (Spitz/Reed) naevus
4. Blue (homogeneous) naevus
5. Site-related naevi
6. Naevi with special features
7. Unclassifiable melanocytic lesions

Globular (congenital) naevus

The globular naevus is characterised dermoscopically by a globular pattern. These lesions are present at birth or arise in childhood, and are likely to be constitutionally predetermined. They persist lifelong.

Age	Clinical features	Dermoscopic features	Histopathology
Childhood	Small: brown, flat, symmetrical, <15 mm.	Brown globules throughout lesion, especially peripheral Areas of hypopigmentation Structureless brown pigmentation obscuring globules	Compound naevus Globules correspond with junctional nests Variable congenital-like features
	Large: flat to elevated with verrucous/hairy surface, >15 mm. True congenital naevi.	Reticular Globular/cobblestone Homogeneous Mixed Perifollicular hypopigmentation
Adult	Elevated, papillomatous Congenital Unna naevus	Cobblestone pattern Fried-egg pattern: globules or structureless centre; peripheral network	Dermal naevus Papillated epidermal hyperplasia Variable congenital-like features

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Reticular (acquired) naevus

The reticular naevus is characterised dermoscopically by a reticular or network pattern of pigmentation. They arise during childhood and adult life, most likely triggered by sun exposure or other factors. They have a tendency to regress in later life and may disappear.

Size	Clinical features	Dermoscopic features	Histopathology
Small	Brown, flat, <15 mm Symmetrical, monomorphous	Regular pigment network Structureless areas (brown or pale)	Junctional or compound Thin, elonged retes ridges Sometimes with dysplastic features
Large	Brown, flat, >15 mm Variable	Multifocal hypo/hyperpigmented areas Sometimes with atypical features, e.g., irregular network

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Starburst (Spitz/Reed) naevus

The starburst (Spitz/Reed) naevus has two distinct dermoscopic patterns. These lesions are uncommon, and may arise in children or young adults. Changing lesions may be difficult to distinguish from melanoma, and should be excised.

Type	Clinical features	Dermoscopic features	Histopathology
Pigmented	Brown to black, flat to elevated, symmetrical Most often face, limbs, buttocks	Starburst pattern Streaks of pigmentation or large globules symmetrically at periphery in radiating pattern	Junctional or compound Heavily pigmented, cohesive, spindle/epithelioid melanocytes Variable epidermal hyperplasia Dermal melanophages
Nonpigmented	Pink to red, dome-shaped, symmetrical	Dotted vessels Reticular depigmentation	Nests of large spindle/epithelioid melanocytes Variable desmoplasia

Blue (homogeneous) naevus

The blue naevus is dermoscopically characterised by homogenous steel blue colour. Blue naevi may be congenital or acquired and are persistent.

Clinical features	Dermoscopic features	Histopathology
Flat to elevated, blue to black	Homogeneous structureless steel-blue colour Variable central or peripheral brown pigment Variable white areas	Heavily pigmented dermal melanocytes Long dentritic processes Thick collagen bundles Several variants

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Site-related naevi

Naevi on palms and soles/nails, and naevi on the face, genitals and nipples have particular dermoscopic features.

Site	Clinical features	Dermoscopic features	Histopathology
Acral	Congenital or acquired Flat to elevated, brown	Parallel pattern Pigment in furrows or lattice-like or fibrillar
Subungual (nails)	Congenital or acquired Uniform pigmented band	Homogeneous brown pigment
Facial	Child: brown, flat, symmetrical Adult: nonpigmented, elevated	Child: pseudonetwork around follicular orifices Adult: comma blood vessels
Lips	Congenital or prepubertal
Nipple	Congenital or prepubertal

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Naevi with special features

This group includes:

• Combined naevi (two types of naevi juxtaposed or merged)
• Halo naevi (uniform lymphocytic reaction)
• Irritated naevi (patchy lymphocytic reaction)
• Cockade naevus
• Naevi with eczematous halo (Meyerson type)
• Recurrent naevi following surgery

Type	Clinical features	Dermoscopic features
Combined naevi	Congenital or acquired Two areas of different colour or size	Two patterns Reticular and globular Reticular and homogeneous Globular and homogeneous Reticular/globular/homogeneous and reticular
Halo naevi	Congenital or acquired Depigmentation in a rim around monomorphous naevus	Globular pattern naevus Variable blue/grey granules White scar-like areas
Irritated naevi	Congenital or acquired Flat to elevated; any colour Peripheral erythema	Reticular/globular/homogeneous Variable blue/grey granules Variable red areas
Cockade naevus	Flat to elevated; at least two colours Central pigmented papule surrounded by inner depigmented and outer pigmented rim	Asymmetric central blue-grey area Surrounded by whitish or erythematous scaly rim Outer rim irregular brown globules
Naevi with eczematous halo (Meyerson type)	Congenital or acquired Flat to elevated; any colour Peripheral eczema	Reticular/globular/homogeneous Variable yellow areas
Recurrent naevi	Congenital or acquired Atypical features Follows incomplete excision or trauma	Atypical pattern of pigmentation Scar-like structures

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Unclassifiable melanocytic lesions

This category comprises atypical or non-diagnostic lesions, which are often clinically or dermoscopically suspicious of melanoma but are not malignant on histology. They may be superficial or nodular.

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Draft 16 November 2008