Diffuse gliomas are the most common malignant primary CNS tumors, classified as astrocytoma or oligodendroglioma based on histologic and molecular features. WHO 2016 updated classification of CNS tumors incorporated molecular markers into the diagnostic criteria. In gliomas, IDH mutation and 1p19q chromosomal co-deletion are the most relevant, early oncogenic, lineage-defining driver mutations with both being present in oligodendrogliomas. Astrocytomas on the other hand can be IDH-mutated (typically in the low-grade setting) or IDH-wild type (typically in high-grade setting). IDH mutant gliomas of either histology are almost exclusively found in patients younger than 55 years old.

59 year-old female hospitalized for a new onset seizure and found to have two discontiguous primarily non-enhancing lesions in the right frontal lobe (superior and supra-orbital). She underwent resection of both lesions without major complications. Pathology results identified the superior lesion as a Grade III astrocytoma (IDH-mutated, 1p19q intact) and the supra-orbital lesion as a Grade II Oligodendroglioma (IDH-mutated, 1p19q co-deleted). Next generation sequencing identified unique molecular alterations in each tumor. She was subsequently treated with radiation to both areas of disease followed by temozolomide chemotherapy.