OLIG2 and glioblastoma: We investigated by immunohistochemistry the clinical significance and the evolution of Oligodendrocyte lineage transcription factor 2 (OLIG2) and cyclin D2 (CCND2) protein expression, two markers highly specific of glioma stem cells, on a cohort of human paired glioblastoma samples comparing initial resections with recurrent tumors after radiation therapy alone or radio‐chemotherapy with temozolomide according to the Stupp regimen.