IDH1 and oligodendroglioma: Because tumors with the trias “IDH/TP53/ATRX” most commonly show an astrocytic differentiation and tumors with the trias “IDH/1p/19q codeletion/TERTp” an oligodendroglial differentiation the designations “astrocytoma” and “oligodendroglioma” were carried on by the WHO to these -by now molecularly defined- tumor types.