Oligodendroglioma

Case contributed by Dr Henry Knipe

Presentation

First seizure.

Patient Data

Age: 50 years
Gender: Male
Modality: CT

Large parenchymal calcification within the medial right parietal lobe deep white matter. Cingulate gyrus appers hypodense and expanded (best seen on coronal images). 

Modality: CT

No appreciable abnormal post contrast enhancement. 

Modality: MRI

Abnormal high FLAIR signal in the right parietal lobe and cingulate gyrus medially with positive mass effect and cortical involvement, which extends anteriorly into the frontal lobe, and into the posterior limb of the internal capsule. The posterior body and splenium of the corpus callosum also appear to be involved, and high FLAIR signal abnormality crosses the midline.

Central in the FLAIR signal abnormality is a large area of susceptibility artifact with few adjacent punctate areas, shown to be calcification on the previous CT brain.

Wispy peripheral enhancement is most conspicuous at the posterior end of the cingulate gyrus.

MRS through the FLAIR signal abnormality demonstrates reversal of the Cho:Cr and depression of NAA peaks. Increased lipid/lactate peaks are also seen.

MR perfusion demonstrates mildly elevated CBV in the right parietal high FLAIR signal deep white matter. 

Histology

MICROSCOPIC DESCRIPTION: The sections show features of a moderately cellular glial tumour. There is a proliferation of neoplastic oligodendroglial cells. They have round nuclei and perinuclear haloes. They extend into the cortex. Rare mitoses are seen, being 1 per 10 high power fields. No microvascular proliferation or necrosis is present. The background shows chicken-wire pattern of blood vessels and with scattered deposits of dystrophic calcification. The features are those of oligodendroglioma.

The tumour cells are focally p53 positive. The topoisomerase index is about 3-4%. IDH1-R132H immunostain is positive (mutated). MGMT is negative (likely methylated). ATRX shows no loss of staining (non-mutated).

DIAGNOSIS: Oligodendroglioma, IDH-mutant (WHO Grade II).

NB: ATRX status and 1p19q co-deletion status are usually inversely related. In this case, ATRX being intact suggests that 1p19q is co-deleted, further supporting the diagnosis, even in light of the 2016 WHO classification of CNS tumour update. 

Case Discussion

The signal abnormality centred in the medial right medial parietal lobe is most consistent with a glial tumour. The calcification on the CT brain indicates that an oligodendroglioma is the likely histological diagnosis. There are some features of high grade tumour such as high CBV and enhancement which are suggestive of a high-grade tumour but these can also occur in low-grade oligodendrogliomas.

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Case Information

rID: 49224
Case created: 16th Nov 2016
Last edited: 24th Nov 2016
Inclusion in quiz mode: Included

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