In line with the model of multi-step tumorigenesis, alterations in oncogenes, in particular BRAF and N-RAS, as well as in tumor suppressor (TS) genes, such as Cyclin-dependent kinase inhibitor 2a (CDKN2a), Phosphatase and Tensin homolog (PTEN) and also TS p53, are required for the transformation process of melanocytes to melanoma cells (reviewed in [3]). The gene discussed is CDKN2A; the disease is melanoma.