Immunoblastic sarcoma of the B-cell type in the CSF. Light- and electronmicroscopic study of the malignant cells and unusual macrophages.

In a patient with systemic and nervous system IBS, the CSF cells were investigated by light and electron microscopy. An IBS of the B-cell type was identified in the CSF which proved, at both morphological levels, to be identical to that recorded in IBS in lymphoid tissue with regard to the malignant cell types and the absence of surface specialization. In contrast, unusual macrophages were observed in the CSF instead of the reticular elements associated with IBS in lymph nodes which present desmosomes. They demonstrated both phagocytosis and emperipolesis and also displayed autodesmosomes. The CSF phagocytes are discussed in relationship with the phagocytes described in the brain with malignant lymphoma.