MACROSCOPIC DESCRIPTION: "Brain tumour": A flat firm piece of brain tissue 30x22x5mm. Serially transversely sectioned and entirely processed.
MICROSCOPIC DESCRIPTION: Paraffin sections show cerebral cortex and white matter which is densely infiltrated by a population of atypical large lymphoid cells. These have round, oval and angulated vesicular nuclei, many with conspicuous nucleoli and a variable amount of pale cytoplasm and are arranged in solid sheets. Aggregation of these atypical cells around blood vessels with invasion of vessel walls is also noted. Frequent mitotic figures are identified. Scattered large reactive astrocytes are admixed with the atypical lymphoid cells.
By immunohistochemistry, the atypical large lymphoid cells are CD20+, CD3-, PAX5+, MUM-1+, bcl-2+. Reactive GFAP+ astrocytes are also noted. EBER-CISH is negative.
DIAGNOSIS: non-Hodgkin's diffuse large B cell lymphoma.