Key Points

• The entity ‘mildly dysplastic naevus’ has been removed from the World Health Organisation’s classification of dysplastic naevi.
• Dysplastic naevi are now to be graded as ‘low grade dysplastic naevus’ (previous moderately dysplastic naevus) or ‘high grade dysplastic naevus’ (previous severely dysplastic naevus).
• Current data suggest no further treatment is necessary for lentiginous junctional/compound naevi and dysplastic naevus with low grade dysplasia (previous mildly dysplastic and moderately dysplastic naevi) with clear histologic margins and no pigment evident clinically, unless there was a high level of prebiopsy clinical concern.
• Re-excision with a 2-5mm clinical clearance is recommended for high grade dysplastic naevi (previous severely dysplastic naevi) with involved histologic margins.
• There is growing evidence that observation may be reasonable for low grade dysplastic naevi (previous moderately dysplastic naevus) if they were excised with clinically clear margins/ no residual clinical pigment is observed, despite histologically involved margins. More data may be required before this is accepted into clinical practice.
• There does not appear to be a clear consensus regarding whether high grade dysplastic (previous severely dysplastic) naevi require re-excision, if initially excised with clear margins, albeit less than 2mm.

Dysplastic naevus: the controversy since the 1970s

The entity of dysplastic naevus has been shrouded in controversy since first described in the 1970s.¹ This appears to be due to: