Presentation
The patient developed symptoms of diabetes insipidus over a period of 2 months.
Patient Data
Contrast-enhanced MRI of the brain reveals a lobulated mass centered in the hypothalamus. There is avid, somewhat heterogeneous enhancement, similar to the pituitary gland. The mass effaces the optic and infundibular recesses, and dorsally displaces the mammillary bodies.
Associated with the mass is expansile, non-enhancing T2/FLAIR signal abnormality. This is observed in the left, greater than in the right, prechiasmatic optic nerves, the optic chiasm, and optic tracts back to the expected location of the lateral geniculate nuclei. Signal abnormality is also seen expanding the right thalamus, right insular cortex, right mesodiencephalic junction, anterior pons, and encasing the mammillothalamic tracts and columns of the fornices. The signal abnormality has subtle but probable continuity, suggesting multifocal tumor.
There is patchy diffusion restriction associated with the pontine signal abnormality, but no significant hemorrhage or calcification is seen on SWI.
Case Discussion
This is an atypical location of multifocal glioblastoma with a dominant hypothalamic mass. The multifocal areas of non-expansile T2/Fluid-Attenuated Inversion Recovery (FLAIR) signal abnormality are clues to the diagnosis of high-grade glioma in this case.
Differential diagnosis:
chordoid glioma (can look identical though it would not explain the additional abnormalities outside the hypothalamus)
diffuse midline glioma (more common in children and young adults but can look identical, needs to be distinguished pathologically)
pilocytic astrocytoma (usually children and young adults and would not expect the other abnormalities outside the hypothalamus and optic pathways)
craniopharyngioma (usually more heterogeneous with cysts and/or calcifications and would not explain the other abnormalities outside the hypothalamus)
germinoma (more common in children and young adults and would not explain the other findings outside the hypothalamus)
ependymoma (usually intraparenchymal when located in supratentorium, 3rd ventricle is rare and would not explain the other findings outside the hypothalamus)
meningioma (rare in 3rd ventricle and would not explain other findings outside the hypothalamus)
The patient underwent biopsy of the hypothalamus.
Histology:
Cellular glial tumor composed of medium sized cells with moderate nuclear pleomorphism and atypia. Pseudopalisading necrosis, microvascular proliferation, and scattered mitotic figures are seen.
Immunohistochemistry and molecular information:
GFAP and Olig2 stains highlight most neoplastic glial cells. The tumor cells are negative for mutant IDH1-R132H. H3K27me3 show variable staining, including a small proportion of cells that show loss of H3K27me3. The Ki-67 proliferation index is up to approximately 10%.
TERT promoter c.-124C>T and PTEN p.S338fs variants; IDH1, IDH2 , or H3F3 variants were not identified; EGFR amplification was not identified; MGMT promoter methylation was detected.
Final diagnosis:
Glioblastoma, IDH-wildtype (by immunohistochemistry), CNS WHO grade 4.
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