Primary CNS lymphoma
The patient went on to have a biopsy.
MICROSCOPIC DESCRIPTION: The sections show cerebral cortex and white matter. There is a prominent band-like infiltrate of atypical large mononuclear cells within the sub-pial molecular layer and a relatively even distribution of similar cells throughout the cerebral cortex with patchy perivascular aggregation. Lesser numbers of the atypical cells are present in white matter. The atypical cells have round, oval and angulated nuclei with an open arrangement of chromatin, conspicuous nucleoli and a variable amount of pale cytoplasm. Frequent mitotic figures are noted. There is a background population of reactive astrocytes.
Immunohistochemistry shows the atypical large cells to be CD20+, bcl-6+, bcl-2+, MUM-1+, CD10-, CD23-, cyclin D1-, CD5-, CD30-, CD68-, CD1a-. Moderate numbers of small CD3+ T lymphocytes are admixed with the large atypical cells. No staining for SV-40/BKV is seen.
In situ hybridization for Epstein-Barr virus (EBER-CISH) is NEGATIVE
FINAL DIAGNOSIS: non-Hodgkin's large B-cell CNS lymphoma (non-germinal center phenotype).