Agminated acquired melanocytic nevi of the common and dysplastic type.

We previously reported a single case of agminated acquired melanocytic nevi, consisting of a localized clustering of banal and atypical moles. We now report 4 more cases, confirming that the initial case was not an isolated finding. We examined the lesions clinically, with a dermoscope, with a Wood's light, and in 3 cases with UV photography so as to exclude nevus spilus from the differential diagnosis. The presence of an underlying dysplastic nevus syndrome phenotype in 4 of the 5 cases raises the possibility that agminated nevi arise as a consequence of postzygotic loss of heterozygosity and, thus, may represent a type 2 segmental manifestation of the atypical mole syndrome phenotype. Further studies of similar cases using microdissection techniques for analysis of loss of heterozygosity pattern are warranted.