Approximately 70–80% of mesothelioma cells have the wild-type p53 gene but show a homologous deletion at the INK4A/ARF locus containing the p14ARF and the p16INK4A genes, which consequently leads to decreased p53 functions despite the wild-type genotype [3]–[5]. The gene discussed is CDKN2A; the disease is mesothelioma.