MICROSCOPIC DESCRIPTION: 5,6,8. Paraffin sections show fragments of leptomeninges in specimens 5 and 6 and leptomeninges and cerebellar cortex in specimen 8. In each specimen there is a population of small to intermediate sized lymphocytes which show strong membrane staining for CD20. These are seen to infiltrate leptomeningeal connective tissue, aggregate around blood vessels and extend into blood vessel walls. Extension of these cells into cerebellar cortex is seen in specimen 8. No viral inclusions or fungal or bacterial organisms are identified. There are no granulomas. The features are strongly suggestive of B cell lymphoma.
DIAGNOSIS: Brain lesion: Lymphocytic infiltrate strongly suggestive of B cell lymphoma in leptomeninges and cerebellar cortex