Oligodendroglioma

KEY FACTS

TERMINOLOGY

• Well-differentiated, slowly growing but diffusely infiltrating

cortical/subcortical tumor

IMAGING

• Most common site is frontal lobe (50-65%)

• Best diagnostic clue: Partially calcified subcortical/cortical

frontal mass in middle-aged adult

○ Typically T2 heterogeneous, hyperintense mass

• ~ 50% enhance

○ Heterogeneous enhancement is typical

• New enhancement in previously nonenhancing

oligodendroglioma suggests malignant progression

TOP DIFFERENTIAL DIAGNOSES

• Anaplastic oligodendroglioma

• Low-grade diffuse astrocytoma

• Ganglioglioma

• Dysembryoplastic neuroepithelial tumor

• Pleomorphic xanthoastrocytoma

• Cerebritis

• Cerebral ischemia

PATHOLOGY

• Loss of heterozygosity for 1p and 19q (50-70%)

• WHO grade II

• Anaplastic oligodendroglioma = WHO grade III

• Oligodendrogliomas carry better prognosis than

astrocytomas of same grade

CLINICAL ISSUES

• 5-10% of primary intracranial neoplasms

• Seizures, headaches, and focal neurologic deficits are most

common presentations

• Peak incidence: 4th and 5th decades

• Median survival time = 10 years

• 1p, 19q deletions and IDH1(+) associated with more

favorable prognosis

(Left) Axial graphic shows a

heterogeneous cystic and solid

mass involving the cortex and

subcortical white matter,

typical of oligodendroglioma.

Note the deep infiltrative

margin ﬈ and calvarial

remodeling ﬉. (Right) Axial

NECT in a 20-year-old man

shows a large, calcified, left

frontal lobe mass ﬈, typical

of oligodendroglioma. The

vast majority (70-90%) of

oligodendrogliomas show

calcification. The calcification

helps distinguish this tumor

from other gliomas,

particularly astrocytomas.

(Left) Axial FLAIR MR in the

same patient shows a

heterogeneous, hyperintense

infiltrative mass expanding

the frontal gyri ſt. The frontal

lobe location and involvement

of both cortex and subcortical

white matter are typical of

oligodendroglioma. (Right)

Axial T1WI C+ MR in the same

patient shows heterogeneous

enhancement ﬊ in this grade

II oligodendroglioma.

Differentiating a grade II from

a grade III oligodendroglioma

is difficult on conventional

imaging. MRS and MR

perfusion may help predict the

tumor grade preoperatively.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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