PTEN and diffuse astrocytoma: In a recent study, 70% of grade II and grade II diffuse astrocytomas were found to possess IDH mutations; IDH-mutant tumors were characterized by frequent p53 abnormalities, PDGFRA expression, and PTEN inactivation by promoter methylation, while IDH-wt tumors were characterized by EGFR amplification, PTEN inactivation by gene copy loss, and enhanced AKT/PI3K signaling [96].