The “early” versus “late” phases of tumor evolution in Type 2 tumors were distinguished by four critical features: (1) the ploidy of tumor cells, cNRT2N-1×-bearing near-2N versus cNRT2N-2×-bearing sub-4N cells; (2) the status of Pten/chr19-normal versus Pten/chr19 loss (or Pik3caH1047R mutation), and associated low versus high levels of PI3K/Akt/mTORC signaling; (3) the relatively quiescent versus high proliferative state of glioma cells; and (4) the localization of tumors to the SVZ versus spatially segregated distant brain parenchyma. Here, PTEN is linked to central nervous system cancer.