The patient went on to have a biopsy.

Histology

MICROSCOPIC DESCRIPTION: \Sections show a hypercellular tumor composed of diffuse sheets of large atypical lymphoid cells. Tumor cells contain abundant amphophilic cytoplasm, oval vesicular nuclei and prominent nucleoli. Frequent mitoses and apoptotic bodies are present. No necrosis or microvascular proliferation are seen.

Immunohistochemical results show tumor cells stain: CD3-, CD20+, CD10-, PAX5+, BCL2+, BCL6+, MUM1+, CyclinD1-, ALK1-, EBERISH-, p53+ (20%), cMYC+ (30%) and Ki67 80%. The features are those of diffuse large B cell lymphoma of activated B-cell (ABC) subtype. 

FINAL DIAGNOSIS: Diffuse large B cell CNS lymphoma