Molecular cytogenetic analysis of Spitz nevi shows clear differences to melanoma

Spitz nevus is a benign neoplasm of melanocytes that can be difficult or im possible to distinguish from melanoma by clinical and histopathologic exami nation, We studied genomic DNA from 17 Spitz nevi by comparative genomic hy bridization (CGH), Thirteen lesions showed no chromosomal aberrations, thre e cases had a gain involving the entire p-arm of chromosome 11, and one cas e showed a gain of chromosome 7q21-qter, Fluorescence in situ hybridization (FISH) on lesional tissue with a probe for the p-arm of chromosome 11 show ed 6-10 p-arm signals per nucleus in those cases with a CGH-detected gain o f chromosome 11p, One case with a normal CGH profile also showed increased copy number of lip by FISH. Thus, the majority of Spitz nevi have a normal chromosomal complement at the level of CGH resolution; however some may con tain gains, with lip apparently being the most frequently involved location . These findings differ significantly from the previously reported changes in primary cutaneous melanoma, which show frequent deletions of chromosomes 9p (82%), 10q (63%), 6q (28%), and 8p (22%), as well as gains of chromosom es 7 (50%), 8 (34%), 6p (28%), 1q (25%) by CGH analysis, These clear differ ences in the location and frequencies of chromosomal aberrations in Spitz n evi and primary cutaneous melanomas could represent a basis for developing adjunctive techniques for refining accuracy in the difficult differential d iagnosis of spitzoid melanocytic neoplasms.