Diffuse Gliomas: O ligodendroglial

Constitute 3% of primary brain tumors and account for about 10% of all gliomas

Peak incidence in fourth and fifth decades of life; children not usually affected

Men slightly more affected than women (1.1 : 1)

Lesions typically arise in the cerebral cortex, usually in the frontal lobe

Because of cortical location, two thirds of patients present with chronic seizures

Other symptoms may include headache and focal neurologic deficits

Median survival is greater than 10 years in some studies, especially with co-deleted chromosomes 1p and 19q

Advanced age carries a worse prognosis

Surgical resection when tumor located in noneloquent brain regions

Chemotherapy and radiation usually reserved for anaplastic tumors

Hyperdense lesion with ill-defined edges on T2-weighted MRI

Hypodense on T1-weighted MRI without contrast enhancement

CT scan will often show calcifications

Soft pink-gray lesion that is ill-defined with blurring of gray-white junction

Calcifications may be present, giving a gritty consistency to the tumor

Monomorphic tumor cells with tendency to form small clusters

Uniform, round, hyperchromatic nuclei

Very low or absent mitotic activity

Perinuclear halos (“fried egg” appearance) are an artifact of formalin fixation: not seen on frozen sections

A delicate, “chicken wire” capillary vasculature is often present

Tumor cell nuclei sometimes form a palisading pattern

Microcalcifications frequently present but not specific

GFAP is variably reactive in tumor cells, but highlights trapped astrocytes

GFAP positive in minigemistocytes and gliofibrillary oligodendrocytes

S-100 positive and usually p53 negative

Ki-67 labeling index is highly variable and dependent upon grade

Mutated form of IDH-1 is immunoreactive in about 75% of oligodendrogliomas

Co-deletion of 1p and 19q associated with better prognosis in about 80% of tumors

Isocitrate dehydrogenase-1 ( IDH-1 ) gene mutations occur in 50% to 80% of low and intermediate grade diffuse astrocytomas and oligodendrogliomas; about 75% of oligodendrogliomas have such mutations

Dysembryoplastic neuroepithelial tumor

Diffuse astrocytoma

Clear cell ependymoma

Demyelinating diseases or other macrophage-rich lesions

Accounts for 1% of all primary brain tumors

20% to 30% of all oligodendroglial tumors are anaplastic oligodendrogliomas

Typically occurs in adults, with peak age of onset 45 to 50 years

Slight male predominance