Mutation analysis has characterised crucial melanoma oncotargets (e.g CDKN2A, BRAF, NRAS, TP53, CDK4, PTEN, NOTCH2)12 and this has already made an impact (e.g. BRAF V600E-targeted therapy), but systematic genome-wide CN analysis would permit a broad range of investigations. The gene discussed is CDKN2A; the disease is melanoma.