IDH2 and astrocytoma (excluding glioblastoma): As mentioned above, IDH mutations, which are specific to astrocytomas and oligodendrogliomas, are characterized by the accumulation of 2-hydroxyglutarate in tumor cells [53,54], while 1p/19q codeletion is observed only on the oligodendroglial histologic subtype and is highly associated with cystathionine levels due to the higher expression of cystathionine-b-synthase (CBS) [55].