Genomic analysis of blue nevi and related dermal melanocytic proliferations

Blue nevi are benign dermal melanocytic proliferations that can sometimes share overlapping microscopic features with melanoma. We used comparative genomic hybridization to analyze three groups of dermal melanocytic proliferations. Group 1 consisted of 10 cellular blue nevi and 1 deep penetrating nevus, none of which showed chromosomal aberrations. Group 2 consisted of 11 lesions that were histopathologically ambiguous. Three of these lesions demonstrated chromosomal aberrations (three or fewer per lesion). Group 3 consisted of seven histopathologically malignant lesions, each showing three or more chromosomal aberrations. Moderate to severe cytologic atypia and a mitotic rate of three or more mitoses per 10 high power fields were present in six of eight (75%) lesions that had at least three chromosomal aberrations but were absent in 15 of 20 (75%) lesions without chromosomal aberrations. Necrosis was present in four of the 29 (13%) lesions, with every lesion with necrosis demonstrating three or more genomic abnormalities. In conclusion, histopathologically unequivocally benign or malignant dermal melanocytic proliferations show nonoverlapping patterns of chromosomal aberrations. Ambiguous lesions can be separated into lesions with and without chromosomal aberrations. Future studies with clinical follow-up are necessary to determine which aberrations are most informative for classification of these lesions.