Presentation
3-month history of headaches with blurred vision. Papillodema on examination.
Patient Data
A non-enhancing isodense lesion is demonstrated in the region of the right thalamus. There is obstructive hydrocephalus of the lateral ventricles.
A homogenous T2/FLAIR hyperintense lesion is demonstrated to the right of the third ventricle. This results in effacement of the third ventricle with associated moderate hydrocephalus and midline shift. Transependymal CSF spread is identified. No contrast enhancement is noted.
Case Discussion
This case demonstrates imaging features of a diffuse midline glioma with associated obstructive hydrocephalus.
The histopathology was confirmed via endoscopic biopsy.
Histology
3rd ventricular lesion: Sections show scanty cellular material composed of spindle to oval nuclei. No definite perivascular pseudo rosettes are seen. No definite mitotic activity is seen within the sparse tissue. No definite papillary architecture. Clear cell morphology, gemistocytic astrocytes or giant cells are not seen. There is no evidence of microvascular proliferation or necrosis. The overall features are of a glial lesion representing a glial neoplasm.
Immunohistochemistry
P53: Probable wild-type pattern of staining.
ATRX: Not interpretable.
H3 K27M: Probable positive showing variable weak to strong staining in most atypical nuclei.
H3 K27me3: Probable negative.
IDH1-R132H: Negative.
BRAF-V600E: Negative
Ki67: Occasional tumor cell nuclei are positive, but the percentage is not able to be given because of the low tumor content.
Comment
Features, in the context of the imaging findings, are those of a diffuse midline glioma, K27M-mutant.
Tissue sections were referred for sequencing, unfortunately, there was insufficient tumor tissue for next-generation sequencing. However, pyrosequencing was attempted and identified the H3 K27M variant consistent with the immunohistochemical results.
Final diagnosis
Third ventricle lesion: Diffuse midline glioma, H3 K27-altered; - WHO grade 4.
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