The patient went on to have a biopsy. 

Histology

MICROSCOPIC DESCRIPTION:

Paraffin sections show cores of cerebral white matter. These show aggregation of large atypical lymphoid cells in cuffs around small caliber blood vessels. Invasion of vessel walls by atypical cells is noted. Atypical cells are also dispersed in white matter between vessels. The atypical cells have large round, oval and angulated vesicular nuclei and a narrow rim of pale cytoplasm. Scattered mitotic figures are identified. Intervening white matter is edematous and shows astrocytic gliosis. The features are of non-Hodgkin's lymphoma.

Immunohistochemistry shows strong membrane staining for CD20 and CD79a and strong perinuclear staining for bcl-2 with weaker staining for bcl-6. There is also strong nuclear staining for MUM-1. Moderate numbers of small CD3+ T lymphocytes are mixed with the atypical large B cells. There is no staining for cyclin D1 or CD23. The features are of non-Hodgkin's large B cell lymphoma.

DIAGNOSIS:

Primary diffuse large B-cell lymphoma of the CNS