Dysembryoeptastic neuroepithelial tumor (DNET) in the setting of Li Fraumeni syndrome
Presentation
Knonwn Li Fraumeni syndrome. Arachnoid cyst on CT. Further assessment.
Patient Data
A 2.5 cm extra-axial, apparently simple cyst is seen to the right of the anterior falx, displacing the adjacent superior frontal gyrus. Arising from the cortex of the displaced gyrus, however, is a non-enhancing, very high T2 partially FLAIR suppressing nodule, with its medial margin outlined by a rim of high FLAIR signal. How it relates to the cys" is unclear. The nodule demonstrates no calcification or no contrast enhancement. ADC values are facilitated (2000 x 10^-6 mm^2/s).
The remainder of the brain is unremarkable in appearance.
Conclusion:
A non-enhancing high T2 cortical exophytic nodule from the right superior frontal gyrus is related to the known 2.5 cm parafalcine cyst. The appearance of the cortical lesion most closely resembles a dysembryoplastic neuroepithelial tumor (DNET). Although this is not a common association with Li Fraumeni syndrome, it is reported. Other lesions with mural nodules (e.g. pilocytic astrocytoma or pleomorphic xanthastrocytomas) would be expected to demonstrate vivid contrast enhancement.
Case Discussion
The patient went on to have a resection.
Histology
Sections show cortical tissue with a vaguely nodular area containing cells with cytoplasmic clearing and centrally located round to oval nuclei with evenly distributed nuclei with microcystic architecture. The background stroma is fibrillary. The microcysts contain amophilic mucinous-type material with floating neurons. Occasional rosette-like structures are seen. No Rosenthal fibers or eosinophilic granular bodies are seen.
Immunohistochemistry
GFAP; Negative
NogoA: Positive
IDH-1 R132H: Negative (non-mutated)
ATRX: Intact (non-mutated)
p53: Patchy positive
p16 CDKN2A: Patchy positive
KI67: <1% The cells are positive for S100 and negative for BRAF V600E.
NeuN highlights neurons floating in microcystic spaces
Final diagnosis
Dysembryoeptastic neuroepithelial tumor (DNET)
Discussion
In the setting of Li Fraumeni syndrome extra care must be taken when discovering any cerebral abnormality due to the high risk of malignancy.
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