Detection of hyperdiploidy and chromosome breakage affecting the 1 (1cen-q12) region in lentigo malignant melanoma (LMM), superficial spreading melanoma (SSM) and congenital nevus (CN) cells in vitro by the multicolor FISH technique.

The centric/pericentric region of chromosome 1 (cen-q 2) of human melanoma cells of different stages of carcinogenicity (superficial spreading melanoma (SSM), lentigo malignant melanoma (LMM)) and premalignant precursor lesions (congenital nevus (CN)) were investigated by fluorescence in situ hybridization (FISH) with tandem DNA probes. The pericentric heterochromatin region 1(q12) is large and highly prone to breakage in contrast to the adjacent centromeric region which is much smaller and less prone to such events. All samples of melanoma cells were obtained from patients and cultivated in vitro. LMM cells showed the highest number of breakage events within the 1q12 region (90% of cells). The number of hyperdiploid cells was not increased in comparison to CN cells. In contrast to LMM cells, SSM cells showed a significant increased number of hyperdiploid cells which were mainly tetrasomic for chromosome 1 (P < or = 0.05). The number of chromosome breaks was not significantly increased in this type of melanoma cells. The spontaneous rates of chromosomal breakage and hyperdiploidy is relatively low in CN cells (1.5-2.5% and 3.2-5.8%, respectively) but these frequencies also differ between CN samples from different patients. These results show that the multicolor FISH technique represents a fast and reliable detection method, distinguishing structural and numerical chromosomal alterations in interphase nuclei. This technique is useful as a histological marker to differentiate between specific tumor subtypes and to investigate the relationship between genomic instability and clinopathological parameters (tumor grading and staging).