Cerebrospinal fluid β2-microglobulin as a diagnostic biomarker in central nervous system lymphoma: a single-center retrospective analysis

This retrospective cohort study investigated the diagnostic performance of cerebrospinal fluid (CSF) β2-microglobulin (β2-M) in patients with central nervous system lymphoma (CNSL). Between January 2018 and August 2024, 1,349 hospitalized patients with CSF β2-M in our center were categorized into lymphoma, leukemia, solid tumor, and other disease cohorts, with additional stratification by central nervous system involvement. CSF β2-M concentrations were markedly elevated in CNSL relative to all other comparator groups ( p  < 0.001). A cut-off value of 1.85 mg/L discriminated CNSL from non-CNS-involved lymphoma with high diagnostic accuracy, yielding 85.7% sensitivity and 89.7% specificity. Longitudinal assessment further demonstrated that dynamic CSF β2-M trajectories correlated with therapeutic response and relapse risk. Collectively, these findings establish CSF β2-microglobulin as a reliable, accessible, and cost-effective diagnostic biomarker for CNSL.