Cytogenetics in hereditary malignant melanoma and dysplastic nevus syndrome: is dysplastic nevus syndrome a chromosome instability disorder?

Analysis of peripheral blood lymphocyte Giemsa-banded karyotypes was performed on 163 family members from 13 melanoma-prone families. Patients were classified regarding the presence of cutaneous melanoma and dysplastic nevi (a well characterized melanoma precursor), and each karyotype was scored for the number of cells containing the following: major structural, minor structural, and numerical abnormalities. No clonal cytogenetic abnormalities were observed. Cutaneous malignant melanoma and dysplastic nevi syndrome patients each had increased abnormalities of all types combined, compared with pooled controls (i.e., normal family members, and spouses; respectively, chi 2 = 6.02, p = 0.01; chi 2 = 5.29, p = 0.02). There was a statistically significant p-value for major structural abnormalities for melanoma patients and numerical abnormalities for the dysplastic nevi patients. Minor structural abnormalities did not differ in any of the groups. In addition, studies of ultraviolet induced sister chromatid exchange, in vitro tetraploidy, and extended prophase banding were performed on a limited number of patients. No significant differences between cases and controls were observed in these tests. Our data suggest that a chromosome instability abnormality may contribute to the pathogenesis of hereditary melanoma.