Primary central nervous system lymphoma (PCNSL) is a non-Hodgkin lymphoma (NHL) affecting the brain, spinal cord, eyes and leptomeninges in the absence of systemic lesions. It represents approximately 3% of primary central nervous system (CNS) tumors and is mainly constituted by diffuse large B cells lymphoma (DLBCL). Nowadays, in most cases, it affects immunocompetent patients. In the past two decades, its prognosis significantly improved due to therapeutic advances but it remains a highly aggressive tumor and early diagnosis for optimal management is a crucial point that may impact outcome [1], [2], [3]. Diagnosis relies on the identification of lymphoma cells in brain tissue obtained by stereotactic biopsy. Alternatively, lymphoma cells may be found in cerebrospinal fluid (CSF) through lumbar puncture in case of meningeal dissemination or by a vitrectomy in case of uveitis, present at diagnosis in up to 20% of cases. For several reasons, the diagnosis of PCNSL may be challenging. Misleading radiological presentations are frequent, mimicking other brain tumors, pseudo-tumoral infectious or inflammatory diseases. Dramatic response to steroids may bias histological analysis and deep brain location or frail health status can contraindicate brain biopsy. Urgent treatment is necessary in some cases. In the follow-up of patients who have been previously treated with high-dose methotrexate based chemotherapy and or intrathecal chemotherapy and/or whole-brain radiotherapy, differential diagnosis between tumor relapse and post-treatment may be also difficult [4]. Therefore, the development of complementary reliable diagnostic tools is needed. Several diagnostic or prognostic CSF biomarkers have been proposed in PCNSL, this review will discuss their interests and limits.

A bibliographic research was conducted with PubMed using the following keywords: CSF BIOMARKER, PRIMARY CNS LYMPHOMA, CNS LYMPHOMA, DIAGNOSIS, PROGNOSIS, and MENINGEAL DISSEMINATION.