TP53 and cerebral astrocytoma: All of these cases also had mutant TP53, and four of the cases had mutant ATRX. Genetically, this group resembles classic IDH1 mutant cerebral astrocytomas, which also usually harbor mutations in TP53 and ATRX. Mean age of these 5 patients was 40 and the predominant tumor location was in the pons, with all 5 having a pontine location, four of which were located both in the pons and medulla.