IDH1 and glioblastoma: Moreover, the use of immunohistochemistry (IHC) for IDH1-R132H, ATRX, and p53 has been employed as a surrogate for genetic status, indicating correlations between histological observations, IHC results, and genetic profiles: (1) IHC for ATRX and p53 should augment morphological diagnosis, (2) consideration of IDH mutations beyond the common IDH1 R132H variant is necessary, and (3) currently, there are no comprehensive substitute assays to fully ascertain the molecular characteristics of GBM as per the 2021 WHO classification [1,19].