The presence of the most common IDH mutation (IDH1 R132H) can be established using immunohistochemistry (IHC) with an antibody highly sensitive and specific for this IDH mutation,6 which accounts for around 85%–90% of the mutations in gliomas.7 If there is suspicion of a rare IDH mutation, the sample would undergo targeted IDH-1/IDH-2 genetic sequencing. The gene discussed is IDH1; the disease is glioma.