Our study confirms, in a large cohort of samples, that CSF is a tissue rich in CD2 CD3 CD5-positive T lymphocytes with a predominance of CD4-positive over CD8-positive T cells (CD4/CD8 ratio = 2), together with a minority of CD56-positive cells in patients with B-cell non-Hodgkin lymphomas negative for leptomeningeal involvement. The gene discussed is NCAM1; the disease is B-cell non-Hodgkin lymphoma.