High incidence of occult leptomeningeal disease detected by flow cytometry in newly diagnosed aggressive B-cell lymphomas at risk for central nervous system involvement: the role of flow cytometry versus cytology

We assessed the cerebrospinal fluid (CSF) by flow cytometry and cytology in 51 newly diagnosed and 9 treated aggressive B-cell lymphomas at risk for central nervous system (CNS) involvement to examine the utility of flow cytometry, incidence of CSIF disease, and clinical surrogates of CNS spread. Multicolor flow cytometry using multiple antibody panels for light chains and B- and T-cell antigens identified neoplastic clones that constituted as little as 0.2% of total CSF lymphocytes. Among 51 newly diagnosed patients, 11 (22%) had occult CSF involvement. All 11 were detected by flow cytometry but only 1 by cytology (P = .002). Among 9 treated patients, CSF involvement was detected by flow cytometry alone in 2 and also by cytology in 1 case. CSIF chemistry and cell counts were similar in patients with and without CSIF lymphoma. Only the number of extranocial sites was associated with occult CSF lymphoma in newly diagnosed patients by univariate (P = .006) or logistic regression analysis (P = .012). We hypothesize that the biologic phenotype associated with colonization of extranocial sites leads to CNS spread, possibly related to the microenvironment. Patients at risk for CNS spread should undergo staging CSF evaluation by flow cytometry. (C) 2005 by The American Society of Hematology.