Olig2, a basic helix-loop-helix transcription factor, plays a role in the specification of oligodendroglia. Reports indicate that Olig2 is expressed in the majority of glial tumors, including oligodendrogliomas and astrocytomas. While over fifty percent of glioblastomas exhibit Olig2 positivity, the expression remains quite low regarding both the number of labeled cells and the intensity of the staining. Olig2 has not been detected in non-glial tumors such as neuroepithelial tumors, ependymomas, subependymomas, medulloblastomas, and non-neuroepithelial tumors like CNS lymphomas, meningiomas, schwannomas, atypical teratoid/rhabdoid tumors, and haemangioblastomas. In contrast to the pronounced staining found in glioma samples, non-tumoral brain tissue (gliosis) shows only weak expression.