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Common and uncommon variants of melanocytic naevi.
Pathology. 2004 Oct;36(5):396-403.
Numerous variants of melanocytic naevi have been described. Their
main pathological significance lies in their distinction from
melanoma, as well as being precursors and risk markers for melanoma.
Various degrees of atypia such as cytological atypia, architectural
disorder and pagetoid spread (pagetoid melanocytosis) may be present
in naevi and need to be recognised as appropriate for the subtype.
As well as the distinction from melanoma, naevi must be
differentiated from atypical lesions, such as atypical Spitz tumours,
which do not fulfil all the criteria of melanoma, may be benign or
malignant and have been called 'melanocytic tumours of unknown
malignant potential'. The diagnostic grey area also includes a group
of benign atypical naevi which are difficult to subclassify into
specific entities. In this paper naevi are divided into: firstly,
the common acquired group with a brief discussion of junctional,
compound and intradermal naevi, minor variants such as halo and
balloon naevi and the major variants that may cause problems --
dysplastic naevi, naevi of special sites, recurrent naevi and Spitz
naevi; secondly, congenital naevi; thirdly, blue naevi and related
lesions (dermal melanocytoses); and finally, combined naevi. The
emphasis is on diagnostic pathological features and the differential
diagnosis with melanoma. |