Oligodendroglioma NOS

Case contributed by RMH Neuropathology

Presentation

Fall at home.

Patient Data

Age: 41
Gender: Male
CT

CT Brain

There is an ill-defined hypoattenuating intra-axial lesion in the anterior aspect right middle frontal gyrus involving cortex and extending into the subcortical and deep white matter of the right frontal lobe. This contains a 9 mm cystic focus and an ill-defined area of hyperattenuation suggestive of calcification.

There is no enhancement following contrast administration.

There is local mass effect: gyral expansion and right frontal lobe sulcal effacement. No midline shift.

Brain parenchyma is otherwise unremarkable.

No evidence of intracranial injury. No skull fracture.

No abnormal enhancement elsewhere in the brain.

Fluid with gas locules in the left maxillary sinus. The remaining visualised paranasal sinuses and mastoid air cells are well-aerated. No bone lesion is demonstrated.

Conclusion: Right frontal intra-axial lesion most probably represents glial series tumour. Calcification, cystic component, and involvement of cortex suggest an oligodendroglial component. Further investigation with MRI should be performed. Findings discussed with the referring ED physician at the time of dictation.

 

MRI

MRI Brain

Within the right frontal lobe there is a region of high signal that predominantly involves the white matter tracts but invades the grey-white matter junction extending into the cortex of the right superior frontal gyrus. This area measures 49 x 40mm and demonstrates high signal on FLAIR and T2. Small foci of T1 post contrast enhancement identified. On DWI and ADC there is patchy diffusion restriction. A central well defined lobular area that is low signal on T1 and high signal on T2 is consistent with a region of cyst formation.

Elevated choline, reduced NAA consistent with glial series tumour, with minimal elevation of lactate suggested on one voxel.

NO elevation of CBV

There is minimal midline shift. No hydrocephalus. The basal ganglia and posterior fossa are normal.

Conclusion: Findings are most likely a right frontal glial series tumour, intermediate grade.​

Pathology

MICROSCOPIC DESCRIPTION: Sections show brain cortex including grey and white matter. There is a moderately cellular tumour replacing white matter and extending into cortex. This is composed of sheets of oligodendroglial cells with round to oval nuclei, coarsely granular chromatin, inconspicuous nucleoli and prominent perinuclear cytoplasmic halos. There is prominent perineuronal, perivascular and sub-pial secondary structuring in cortex. There are thin capillaries with a "chicken-wire" arrangement and microcalcification is also noted. No necrosis or microvascular proliferation are seen. There is an occasional mitotic figure.

IMMUNOHISTOCHEMISTRY:

  • GFAP negative in oligodendroglial tumour cells; positive in reactive astrocytes.
  • NogoA positive in oligodendroglial tumour cells
  • Nestin positive (low)
  • IDH-1 R132H positive (mutated)
  • ATRX positive (not mutated)
  • MGMT negative (likely methylated)
  • p53 negative p16
  • CDKN2A positive
  • Topoisomerase labelling index: Approximately 10%

DIAGNOSIS: IDH-1 mutated Oligodendroglioma (WHO Grade II).

Note: although this case predates the 2016 WHO classification of CNS tumours update and  1p19q codeletion status has not been assessed, the fact that ATRX is positive (not mutated)  suggests that 1p19q would be co-deleted. Unfortunately, this is not enough (the "blue book" goes out of its way to stress this) and this tumour would be classified as oligodendroglioma NOS

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Case information

rID: 40479
Case created: 22nd Oct 2015
Last edited: 2nd Jul 2017
Inclusion in quiz mode: Included

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