Figure 1. Progression and genetic alterations in human malignant gliomas.

Astrocytoma may arise from astrocytes or progenitor cells that accumulate genetic alterations and become transformed. IDH1 and TP53 mutations are believed the first alterations occurring in these tumors. Oligodendrogliomas can develop from the same progenitor cells or mature oligodendrocytes that acquire a distinct set of genetic changes. The earliest changes that occur include IDH1 mutation and a 1p/19p loss. Representative genetic changes are shown with the estimated frequency of occurrence within each type of tumor. OE, overexpression; mut, mutation; del, deletion; met, promoter methylation; amp, amplification.