A significant presence of lymphocytes has been documented, together with floating malignant cells, in CSF samples from patients with non-Hodgkin lymphomas and breast cancer leptomeningeal metastasis (18, 19); an active mechanism of reactive CD8 T-lymphocyte migration has been observed in primary central nervous system lymphomas (PCNSL) of B-cell type (20, 21). The gene discussed is CD8A; the disease is primary central nervous system lymphoma.