Presentation
Headache for two weeks and confusion.
Patient Data
Large heterogeneous intra-axial mass involving grey and white matter (but with extensive cortical involvement) occupies the entire right temporal lobe, including the mesial temporal lobe and extends into the insula, right basal ganglia, right frontal operculum, right parietal, and right occipital lobes.
The lesion is predominantly FLAIR hyperintense with regions of susceptibility-related signal loss consistent with calcification on the phase component of SWI. Many of these areas demonstrate intrinsic high T1 signal. Taking this into account there is minimal if any whispy contrast enhancement. No nodular contrast enhancing component.
Marked elevation of relative cerebral blood volume within the lesion. Marked elevation of choline with depression of NAA in the lesion.
There is marked mass effect with diffuse sulcal effacement in the right hemisphere, and almost complete effacement of the right lateral ventricle with midline shift obstructing the outflow of the left lateral ventricle at the level of the foramen of munro. There is prominent left-sided transependymal edema.
The right uncus, which is also expanded by tumor, herniates medially and compresses the midbrain.
Conclusion:
Features are those of an adult-type diffuse glioma. On imaging grounds alone it most likely represents an oligodendroglioma although it should be noted that IDH mutations are uncommon in this age group.
CT demonstrates that the mass has extensive calcification, further supporting the diagnosis of oligodendroglioma.
Case Discussion
The patient went on to have debulking.
Histology
Sections show a moderately cellular glial tumor composed of sheets of tumor cells with a "chicken-wire" capillary network and scattered psammomatous microcalcification. Tumor cells demonstrate perinuclear cytoplasmic clearing, hyperchromatic round-to-oval nuclei with vesicular chromatin and inconspicuous nucleoli. There is prominent secondary structuring with perineuronal satellitosis and subpial condensation of tumor cells. There are up to 8 mitoses per 10 hpf. No necrosis or microvascular proliferation are seen.
Immunohistochemical results show tumor cells stain:
GFAP Negative
Nestin Low
NogoA Positive
IDH-1 Positive (mutated)
ATRX Positive (not mutated)
MGMT Negative (likely methylated)
p16 Positive
p53 Negative
Topoisomerase proliferation index 10%.
1p19q codeletion detected.
FINAL DIAGNOSIS:
Oligodendroglioma, IDH-mutant, and 1p/19q-codeleted (WHO CNS5 grade 3)
Discussion
As of the 2016 WHO classification of CNS tumors to be designated an oligodendroglioma a tumor must be shown to have both IDH mutation and 1p19q codeletion. Also note, that an oligodendroglioma cannot ever be called a glioblastoma.
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