Dysplastic Naevi
Dysplastic naevus
Note the size, irregular edge and irregular pigmentation.
Features
Clinically, Atypical moles are defined as having: "ill-defined or irregular borders; irregular pigmentation; a diameter >5mm; erythaema and accentuated skin markings."
They are a marker of increased risk of melanoma in both familial and sporadic development. Atypical naevi can be divided into four groups (A-D) on the basis of personal and family involvement. Those with lesions in the A and B categories are 90 times more likely to develop a malignant melanoma than the general population. Those with category D lesions are 400-500 times more likely to develop a melanoma.
Incidence
Common. Estimated prevalence 2-4% of the population.
Aetiology
Can be congenital or acquired. Some families have a tendency to develop atypical naevi.
Differential Diagnosis
Malignant melanoma. Spitz naevus. Junctional naevus.
Treatment
Good evidence exists that if atypical naevi are observed closely in a specialist centre for any signs of malignant change, tumours will be diagnosed earlier. As atypical naevi are a marker for increased melanoma risk, all of the skin should be checked regularly.
