A role for p53 inactivation in MB pathogenesis is suggested by the increased incidence of MB in people with Li Fraumeni syndrome, which is caused by germ-line mutation in p53[28], [29], as well as in rodent models in which p53 is co-deleted with genes such as Ptch1[30], [31]. The gene discussed is TP53; the disease is Li-Fraumeni syndrome.