The melanoma cell lines showing a higher copy number than expected from the Grey genotype, Ho-Mel-A1 (Seltenhammer et al., in preparation) and M14 [20], have both been characterized as malignant, with M14 showing a high expression of the proliferating cell nuclear antigen PCNA [20], previously correlated with aggressive behaviour of human cutaneous malignant melanoma [19]. The gene discussed is PCNA; the disease is melanoma.