In cases that are not immunoreactive for IDH1 R132H, but ATRX nuclear expression is lost, and the p53 staining pattern is indicative of a mutation, a non-canonical IDH1 or IDH2 mutation should be suspected, and sequencing should be pursued, particularly if the patient is younger than 55 years of age and/or the tumour has a lower grade histology [8]. The gene discussed is IDH2; the disease is neoplasm.