For example, the 2016 WHO brain tumour classification delineated GBM into IDH‐wild‐type (IDH‐WT; ∼90%) or IDH‐mutant (∼10%), with the latter associated with better overall survival and increased sensitivity to temozolomide.1, 10, 11, 12, 13. The gene discussed is IDH1; the disease is glioblastoma.