IDH1 and oligodendroglioma: Based on the IDH mutation and 1p/19q codeletion status, LGGs are classified into three diagnostic and prognostic subtypes in the 2016 WHO classification: IDH wild‐type (holding the worst outcome), IDH mutant and 1p/19q intact, and IDH mutant and 1p/19q codeleted tumors (oligodendrogliomas) (Louis et al., 2016).