Serum miR-21 is a diagnostic and prognostic marker of primary central nervous system lymphoma.

The standard of care for primary central nervous system lymphoma (PCNSL) is systemic chemotherapy with or without whole brain radiotherapy or intrathecal chemotherapy. In contrast to treatment for other brain tumors, efforts at resection are discouraged. However, it is difficult to distinguish PCNSL from other central nervous system tumors which need aggressive surgery in both CT and MRI images. In this study, we assessed whether measurement of miR-21 in the serum could improve diagnostic accuracy for PCNSL. We found that serum miR-21 significantly increased in PCNSL when compared with other brain tumors and normal controls in both test and validation cohort. Further, serum miR-21 could discriminate PCNSL from all controls with an area under the curve of 0.930 for the test cohort and 0.916 for the validation cohort in ROC analysis. Similar results were also obtained in the validation cohort. Besides, raised concentrations of miR-21 in serum could differentiate PCNSL from glioblastoma under the curve of 0.883 for the test cohort and 0.851 for the validation cohort in ROC analysis. Furthermore, Kaplan-Meier curve analysis (p = 0.03 for test cohort and 0.02 for validation cohort) and Multivariable Cox regression (p = 0.03 for test cohort and 0.01 for validation cohort) revealed serum miR-21 as an independent and powerful predictor of overall survival. Taken together, our results demonstrate that serum miR-21 may represent a diagnostic and prognostic marker for PCNSL.