As the vast majority of IDH mutations in gliomas occur in the IDH1 R132 residue [9,10], immunohistochemical stains specific for mutant IDH1 R132H protein were developed as a molecular surrogate to aid in rapid and lower-cost detection of this key mutation [11,12], with the added benefit of assisting in differentiating between neoplastic and non-neoplastic astrocytes [13,14]. The gene discussed is IDH1; the disease is glioma.