INTERPHASE CYTOGENETICS OF MELANOCYTIC NEOPLASMS - NUMERICAL ABERRATIONS OF CHROMOSOMES CAN BE DETECTED IN INTERPHASE NUCLEI USING CENTROMERIC DNA PROBES

This study shows that fluorescence in situ hybridization (FISH) to thi n sections cut from paraffin-embedded material can be used to distingu ish between groups of melanocytic neoplasms and thus may be useful as an investigational and diagnostic tool. FISH with a probe for a repeat ed, alpha satellite sequence specific to chromosome 17 was used to inv estigate the chromosomal composition of dysplastic (or Clark's nevus) and Spitz's nevi and malignant melanomas. Hybridization was to thin (a pproximately 6 mum) sections cut from paraffin blocks. The number of s ignals per nucleus in normal diploid cells is expected to be less than 2 since the sections are thinner than one nuclear diameter. Keratinoc ytes and lymphocytes in these same sections showed 1-2 signals per nuc leus with a mean of 1.2. Dysplastic nevi showed 1-4 hybridization sign als per nucleus with a mean of 1.5. Spitz's nevi showed 1-2 signals pe r nucleus with a mean of 1.3. Melanomas showed 1-6 signals per nucleus with a mean of 2. 1. We were thus able to use FISH to demonstrate dif ferences in chromosome numbers between groups of benign and malignant melanocytic neoplasms. Technical improvements in the near future can b e expected to result in more precise estimates of chromosomal number.