Presentation
3 generalized tonic clonic seizures
Patient Data
Selected FLAIR and T1 C+ images demonstrate a small region of high T2 involving the cortex and subcortical white matter of the precuneus, without contrast enhancement. This was felt to most likely be a low grade glioma, or potentially a region of focal cortical dysplasia. Follow-up imaging was organized.
Selected FLAIR and T1 C+ images demonstrate surprisingly fast growth with faint punctate enhancement now visible. Findings are suspicious for progression to a higher grade.
The patient was reviewed as an outpatient a few weeks later. Given the fairly rapid growth, the decision was made to biopsy this lesion and a stereotaxis scan was organized.
Selected FLAIR and T1 C+ images from stereotaxis scans for operative planning demonstrate still further growth and increase in enhancement.
MICROSCOPIC DESCRIPTION:
Paraffin sections show multiple fragments of a densely hypercellular tumor. Tumor cells have pleomorphic round, oval and angulated hyperchromatic nuclei with fibrillary processes. Moderate numbers of mitotic figures are identified (8 in 20 high power fields). Foci of microvascular proliferation with multilayering of atypical cells around vessel lumena are noted and there are scattered foci of palisaded necrosis. There is patchy microcalcification.
IMMUNOHISTOCHEMISTRY:
- GFAP: positive
- Nestin: positive (high)
- IDH-1 R132H: negative (not mutated)
- ATRX: positive (not mutated)
- p53: positive
- p16 CDKN2A: positive
- MGMT: positive (likely unmethylated)
Topoisomerase labeling index: Approximately 40%.
DIAGNOSIS: Glioblastoma (WHO Grade IV)
Case Discussion
This case illustrates the difficulty conventional imaging has in distinguishing a low-grade tumor with indolent biological behavior from early imaging of a more aggressive tumor. In this case were a biopsy to have been performed at the time of the first scan it would almost certainly have demonstrated a diffuse low-grade glioma. At that stage, however, it would have been IDH negative, which would have been predictive of aggressive behavior.
Although the very aggressive behavior is entirely consistent with IDH wild-type molecular subtype, as is MGMT being unmethylated 1, to conclusively establish this IDH would need to be sequenced to ensure that a non-IDH1 R132H mutation was present. This is particularly relevant in young patients.
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