PTEN and PTEN hamartoma tumor syndrome: The experimental evidence that loss of p53 function, but not Pten or Rb, contributes to early stages of gliomagensis in mice is consistent with the elevated incidence of astrocytomas in individuals with Li-Fraumeni syndrome but neither in Pten Hamartoma Tumor Syndrome (PHTS) nor in patients with germline RB1 mutations [54-56].