ATRX and astrocytoma (excluding glioblastoma): When comparing pathological and molecular findings with the three molecular classes (Table 2), ATRX down-regulation was mainly restricted to astrocytomas IDHmt (p < 0.0001), and the fraction of p53-positive tumors was 90.4% in astrocytomas IDHmt vs. 46.2% in astrocytoma IDHwt and 35.7% in oligodendrogliomas (p < 0.0001).