IDH1 and astrocytoma (excluding glioblastoma): This is exemplified by the fact that IDH wild-type infiltrative astrocytomas with a lower histologic grade have a similar prognosis to that of (Grade IV) GBM.  Additionally, these studies confirm that lower-grade gliomas with an IDH mutation have either 1p/19q co-deletion or a TP53 mutation, with few gaps or overlaps, reflecting two distinct molecular mechanisms of oncogenesis.