Oligoastrocytomas

Oligoastrocytoma is a historical diagnosis for a diffuse glioma in which tumor cells show both oligodendroglial and astrocytic differentiation on histology.

Histology: the tumor contains areas with oligodendroglial-like cells—round nuclei with clear perinuclear halos—and areas of astrocytic cells with elongated, GFAP-positive processes. Calcifications, microcysts, mitotic activity, necrosis, and microvascular proliferation may be present, and grade is assigned accordingly.

Clinically these tumors occur in adults, typically in the cerebral hemispheres, presenting with seizures or focal neurological deficits. Prognosis is variable and depends on factors such as age, extent of resection, tumor location, and molecular features.

Since the WHO classification emphasizes molecular features, the term oligoastrocytoma is used less; many tumors previously labeled this way are now classified as astrocytoma, IDH-mutant (with or without 1p/19q codeletion) or oligodendroglioma, IDH-mutant with 1p/19q codeletion. Cases with uncertain results may be designated oligoastrocytoma, NOS.

Diagnosis and management rely on histology plus molecular testing and MRI imaging. Treatment generally includes maximal safe surgical resection when feasible, followed by radiotherapy and chemotherapy (such as temozolomide or, for oligodendroglioma, regimens including PCV) depending on molecular subtype and grade. Prognosis varies accordingly, with outcomes more favorable for tumors with certain molecular profiles.