Diagnosis of central nervous system (CNS)
lymphoma depends on histopathology of brain biopsies, because no reliable disease marker in the cerebrospinal fluid (CSF) has been identified yet.
B-cell lymphomas such as CNS
lymphomas are clonally restricted and express either kappa or
lambda immunoglobulin light chains. The aim of this study was to find out a potential diagnostic value of free
immunoglobulin light chains released into the CSF of CNS
lymphoma patients. Kappa (kappa) and lambda (lambda) free
immunoglobulin light chains (FLC) were measured in CSF and serum samples collected from 21 patients with primary and secondary CNS
lymphomas and 14 control patients with different
neurologic disorders. FLC concentrations and ratios were compared between patient groups and were further analyzed in correlation with clinical, cytopathological, and radiological findings. FLC concentrations for all patients were lower in CSF when compared to serum. In patients with CNS
lymphoma, the FLC ratios in CSF were higher (range 392-0.3) compared to control patients (range 3.0-0.3). Irrespective of cytopathological proven lymphomatous
meningitis, in 11/21
lymphoma CSF samples the FLC ratios were markedly above 3.0 indicating a clonally restricted B-cell population. Increased FLC ratios in CSF were found in those patients showing subependymal
lymphoma contact as detected in magnetic resonance imaging. In summary, this is the first report demonstrating that a significant proportion of patients with CNS
lymphomas display a markedly increased FLC ratio in the CSF.