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Background: Cytologic evaluation of CSF does not consistently detect malignant cells in patients with primary CNS lymphoma (PCNSL). The potentially more sensitive molecular assessment of monoclonality has not been shown in CSF samples.

Methods: The authors studied nested PCR of the complementary determining region III (CDR III) on 76 CSF specimens of patients with PCNSL. Patients with systemic disseminated B-cell non-Hodgkin's lymphoma (n = 17) and 17 patients with no history of lymphoma were compared. PCR products were evaluated by automated fluorescent fragment analysis (ALF).

Results: In 68 patients with PCNSL, the authors analyzed the first obtained CSF sample. Nevertheless, 60 patients were taking corticosteroids. In 16 PCNSL samples, amplifiable DNA was not yielded. Taking into account that at least two independent assays have to be performed, CDR III PCR consistently revealed monoclonal products in eight PCNSL and polyclonal results in 52 PCNSL specimens. CDR III PCR detected no monoclonal PCR products in patients without history of lymphoma. In 10 patients with PCNSL, the PCR result and the CSF cytology were discordant. Concerning therapeutic impact, leptomeningeal tumor spread did not predict tumor response in this group of patients with PCNSL.

Conclusions: This study performed CDR III PCR as a routine diagnostic technique applicable even on CSF samples with low cell counts. These data present low incidence of leptomeningeal involvement in this subset of pretreated PCNSL patients. Because the CSF evaluation did not predict outcome in our patients, further analysis in patients with PCNSL should focus on CSF samples that are obtained very early after diagnosis.

(C) 2002 American Academy of Neurology