Dysplastic naevi are large, active, typically truncal naevi, commonly seen in adults. They may be single or multiple, are usually larger than 5 mm diameter, and may have an irregular edge, irregular pigmentation, or may show signs of inflammation.
They may be familial or sporadic. Dysplastic naevi are more likely than ordinary moles to undergo malignant transformation, though most dysplastic naevi are clinically stable. Wholesale excision of dysplastic naevi is therefore not recommended (1).
Histologically dysplastic naevi are similar to compound naevi, though they demonstrate cytological and architectural signs of atypia.
Dysplastic naevi can overlap clinically with the widely used ABCD (Asymmetry, Border irregularity, Colour variegation, Diameter>6mm) criteria for melanoma. But the changes in dysplastic naevi are present to a lesser degree. In serial photographic follow-up, dysplastic naevi are stable, or may even regress. Thus, they do not fulfil the ‘E’ criterion (Enlargement). Similarly, they don’t show other signs such as increase in elevation, development of a nodule, bleeding, or ulceration (1).
Studies have shown that some small (<5 mm) naevi too display cytological and architectural features indistinguishable from that of classic dysplastic naevi. It is suggested that a histological diagnosis of dysplastic naevus should only be applied to relatively large (>5-6 mm) naevi (2).
Dysplastic naevi are also known as BK moles after the two families in which the familial types were originally studied.
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