IDH1 and oligodendroglioma: The latter is an IDH mutant tumor composed of two distinct populations, showing the morphological features and genotype of astrocytoma (TP53 mutation/nuclear p53 accumulation, loss of nuclear ATRX expression and absence of 1p/19q codeletion) or oligodendroglioma (lack of TP53 mutation/nuclear p53 accumulation, retained nuclear ATRX expression and 1p/19 codeletion) [1,14].