The imaging findings were suggestive but not specific for a high grade glioma of the optic pathway. Differential considerations included lymphoma and metastases. Inflammatory disorders such as neuromyelitis optica were felt to be less likely given how expansile the lesion was.

A broad serum and CSF infectious and inflammatory workup was negative. CSF cytology was negative for malignant cells as well as IGH rearrangement and MYD88. Whole body PET, total spine MRI, and testicular ultrasound revealed no other sites of disease (not shown). The patient received empiric high dose steroids without improvement in vision but improvement of MRI findings. Empiric treatment for primary CNS lymphoma was undertaken consisting of palliative radiation and high dose methotrexate.

Following a decline in functional status and an episode of unresponsiveness concerning for seizure, biopsy was undertaken of the third ventricular lesion.

Pathology:

• Integrated diagnosis: glioblastoma, CNS WHO grade 4

• Histological diagnosis: anaplastic astrocytoma

• Molecular information

  • IDH: negative (PCR)

  • ATRX: retained nuclear staining (immunohistochemistry)

  • p53: diffuse moderate positive staining (immunohistochemistry)

  • BRAF V600E: negative (immunohistochemistry; consistent with wild type)

  • H3K27M: negative (immunohistochemistry; consistent with wild type)

  • EGFR: amplified (FISH)

  • TERT promoter: mutant (Snapshot next-generation sequencing)

  • MGMT promoter methylation: positive

Glioblastoma of the optic chiasm is rare. Diagnosis is challenging due to inaccessibility for biopsy. The prognosis is poor. This patient died less than 4 months after initial presentation.