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1、http://www.emedicine.com/derm/topic903.htmCongenitalNeviLastUpdated:August23,2005Author:ChristopherJSteen,MD,JerryRothenbergMD;IsabelleThomas,MD,RobertASchwartz,MD,MPHBackground:Congenitalneviarepresentatbirthandresultfromaproliferationofbenignmelanocytesinthede
2、rmis,epidermis,orboth.Occasionally,nevithatarenotpresentatbirthbutarehistologicallyidenticaltocongenitalnevimaydevelopduringthefirst2yearsoflife.Thisisreferredtoascongenitalnevustardive(Clemmensen,1988).Congenitalneviareoneofseveralknownriskfactorsfortheeventual
3、developmentofmelanoma.Fortunately,melanomaremainsanuncommonmalignancyinprepubertalchildren,withanannualincidenceof0.7casespermillionchildrenaged0-9years.Patientconcernsregardingchangingorworrisome-lookingneviare,nonetheless,verycommon.Moreover,bythetimeachildrea
4、chesadolescence,theincidenceofmelanomaincreasessubstantially,witharateof13.2casespermillionchildrenaged15-19years.Whilemanysourceshavenotedtheso-calledmelanomaepidemicinadults,onlyinrecentyearshavedatadocumentedanalarmingincreaseinmelanomainadolescents.Thisincre
5、ase,combinedwiththerecognitionofclearlyidentifiablemelanomariskfactorsinchildhood,allowsphysiciansofthe21stcenturytoplayacrucialroleintheidentificationofchildrenatriskformelanomaandtoaidinthepreventionofmelanomathrougheducationregardingtherisksofultravioletlight
6、exposure.Pathophysiology:Theetiologyofcongenitalmelanocyticneviremainsunclear.Themelanocytesoftheskinoriginateintheneuroectoderm,althoughthespecificcelltypefromwhichtheyderiveremainsunknown.Onehypothesisisthatpluripotentialnervesheathprecursorcellsmigratefromthe
7、neuralcresttotheskinalongparaspinalgangliaandperipheralnervesheathsanddifferentiateintomelanocytesuponreachingtheskin(Cramer,1988).Onepossibleexplanationforthepresenceofcongenitalmelanocyticneviisthatanexternalinsultresultsinamutationthataffectsthemorphogenesiso
8、ftheembryonicneuroectodermandmigrationofprecursorcellstotheskin.10Congenitalnevihavebeenstratifiedinto3groupsaccordingtosize.Smallneviarelessthan1.5cmingreatestdiamet
