GPT and oligodendroglioma: The ALT-negative and TERTp-mutant oligodendroglioma PDCs had telomeres ranging from ~2 to 6 kb, consistent with maintenance of critically short telomeres, while ALT-positive astrocytoma PDCs had a more heterogeneous distribution of telomere lengths that included an accumulation of much longer telomeres at 18.8 kb (Figure 3C).