The brain lesion has been also biopsied: 

MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of cerebral cortex and white matter. These show perivascular accumulation of small lymphoid cells around small caliber blood vessels, predominantly in white matter, but also focally within cortex. Lymphoid cells are CD4>CD8 T lymphocytes with smaller numbers of CD20+ B lymphocytes and CD68+ monocyte-macrophages. There is widespread microglial activation and astrocytic gliosis. No atypical lymphoid cells are identified. There are no granulomas and no evidence of demyelination is seen. There is no evidence of tumor. Immunostaining for IDH-1 R132H is negative. Cortical lamination is preserved. There is no polioclasis and no microglial nodules or viral inclusion bodies are seen. There is no spongiform change. Immunostaining for A-beta protein is negative. No plaques or neurofibrillary tangles are identified and there are no ubiquitin glial inclusions. Moderate numbers of neurons are noted in white matter.

DIAGNOSIS: Brain biopsies: T lymphocytic angiotropic inflammatory changes consistent with cerebral angiitis, viral encephalitis or auto-immune encephalitis.

This patient was later diagnosed with a primary testicular cancer.