Molecular analysis of the CDR3 encoding region of the immunoglobulin heavy chain locus in cerebrospinal fluid cells as a diagnostic tool in lymphomatous meningitis.

The diagnosis of leptomeningeal B-cell lymphoma is based on the identification of malignant B cells in the cerebrospinal fluid (CSF). Frequently, cytology does not allow clear distinction between neoplastic lymphoid cells and reactively transformed mononuclear cells. Individual B-cell clones can be identified on the basis of DNA sequences that encode the highly diverse complementarity-determining region (CDR3) of the immunoglobulin heavy chain locus (IgH). We studied CSF samples from 5 patients with B-cell malignancies and cytological evidence of leptomeningeal involvement, using polymerase chain reaction (PCR)-based high-resolution capillary electrophoresis and automated fluorescence analysis to detect PCR fragments. As controls, we assessed CSF specimens from 7 patients with inflammatory neurological diseases and three samples without pathological findings. In all patients with B-cell malignancies, a single PCR product was generated, indicating that CDR3-specific fragments were derived from monoclonal cell populations. CSF samples from patients with inflammatory diseases yielded multiple CDR3 amplicons, suggesting the presence of a polyclonal B-cell activation. No PCR product could be amplified in normal CSF samples. Automated fluorescence detection of CDR3 fragments is a highly sensitive and rapid method to distinguish neoplastic monoclonal and reactive polyclonal B-cell populations in the CSF.