GP Quiz 28 – Case 1
What is the clinical term used to describe this lesion?
Dysplastic naevus
What are its distinguishing features?
The dysplastic naevus is greater than 5 mm in diameter, often has a fading border, uneven distribution of colour (often including red) and an irregular shape. It is frequently misdiagnosed but appears to markedly increase the risk of melanoma in that individual, which may arise within a pre-existing benign lesion or de novo. Pathologically true dysplastic naevi have architectural disorder and cytological atypia, and they show genetic instability. These are the precursor lesions in familial melanoma.
The term 'dysplastic naevus' means different things to different clinicians and pathologists. It is often replaced by the term 'atypical naevus', which may also be used to indicate any mole that looks unusual. The more unusual-looking the mole, the greater the clinical and histological confusion with melanoma.
Describe the dermoscopic features of concern.
Dermoscopy shows an irregular tan pigment network with some focal peripheral streaks (top left). Crossing the lesion is a darker, rather hazy, greyish network. There are patchy pale blotches with a suggestion of regression.
This appearance could also arise in melanoma in situ; the histology revealed moderate atypia.
This quiz was also published by New Zealand Doctor in Sept 2005.