Interphase cytogenetic analysis of 1q12 satellite III DNA in melanocytic lesions: increased aneuploidy with malignant histology.

To examine the relationship of chromosome 1 copy number to melanocytic tumorigenesis, interphase cytogenetic analysis of 1q12 satellite III DNA was performed on the spectrum of melanocytic lesions comprising Clark's tumor progression model. Results showed increased copy number in a "step off" pattern between melanoma in-situ and the intraepidermal component of invasive melanoma rather than a progression between each lesional group. These findings support Clark's concept of independent clonal expansion of a cell population giving rise to the vertical growth phase and further demonstrates increased chromosome 1 copy number as a late event in melanoma tumor progression.