Presentation
History of migraine.
Patient Data
Technique: Multiplanar, multisequence imaging has been obtained through the brain including pre and post contrast sequences, MR perfusion and MR spectroscopy.
Comparison: Outside scan from one month ago.
Findings: An area of signal change on the FLAIR and T2 with slight positive mass effect is identified in the medial and anterior aspect of the superior left frontal gyrus. Signal change extends into the cortex which is also is thickened.
A leading-edge of signal abnormality extending down to the ventricle is not clearly identified but would necessitate high-resolution 3-D FLAIR imaging
No contrast-enhancement in associated with the lesion. No raised cerebral blood volume (CBV). MR spectroscopy shows a decrease of metabolites without increased choline and without increased myoinositol peak.
No other lesions are identified
Conclusion: An area of signal abnormality with mass effect is present within the superior frontal gyrus on the left. Differential diagnosis lies between cortical dysplasia and low-grade glioma. Spectroscopic findings would favor cortical dysplasia.
MICROSCOPIC DESCRIPTION: The sections show cerebral cortex and white matter. Cortical laminar architecture is preserved with no features of cortical dysplasia seen. There is prominent perineuronal secondary structuring. White matter contains a population of atypical glial cells with oligodendroglial morphological features - enlarged round and oval hyperchromatic nuclei, some with perinuclear clearing and a paucity of processes. Several groups of overlapping nuclei are noted. No mitotic figures are identified. There is no microvascular proliferation and no necrosis is seen. A population of reactive astrocytes is also present.
IMMUNOHISTOCHEMISTRY: GFAP negative in atypical oligodendroglial cells; positive in reactive astrocytes. NogoA positive in atypical oligodendroglial cells. IDH-1 R132H positive (mutated) ATRX positive (not mutated) p53 negative MGMT positive (likely unmethylated) p16 CDKN2A positive Topoisomerase labeling index: Approximately 1%. The features are of IDH-1 mutated diffuse glioma (WHO II) strongly favoring oligodendroglioma.
DIAGNOSIS: IDH-1 mutated diffuse glioma (WHO II) with features strongly favoring oligodendroglioma.
Case Discussion
This case demonstrates a small cortical lesion that is a real challenging for radiologists, even with all the MRI advanced sequences available. The histology confirmed a diffuse glioma most likely representing an oligodendroglioma (WHO grade II).
Typical MRI features for this kind of tumor were not present, and the appearance was indistinguishable from a cortical dysplasia.
Note: This case predates the recent (2016) revision WHO classification of CNS tumors, and thus molecular markers (IDH mutation and 1p19q co-deletion) are not available. As such, this tumor would now be classified as an oligodendroglioma NOS.
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