IDH1 and oligodendroglioma: This patient, while identified during our review as having an IDH mutation discrepancy, also had a documented 1p/19q codeletion at time of initial surgery, which is mutually inclusive of having an IDH mutation.1 Therefore, this patient was originally treated as an IDH mutant oligodendroglioma despite the negative IHC testing and does not represent a case of IDH mutation discrepancy.