Primary central nervous system lymphoma (PCNSL) is a rare hematological malignancy, affecting the central nervous system (CNS), meninges, or eyes. Advancements in treatment, particularly with IV high-dose methotrexate, have improved patient survival. Diagnosis is primarily based on contrast-enhanced brain MRI, followed by confirmation through brain biopsy. However, biological markers such as cerebrospinal fluid (CSF) or vitreous humor lymphocyte immunophenotyping and interleukin levels (IL-6 and IL-10) can aid diagnosis, especially in cases where biopsy is difficult.

This retrospective observational study examines the diagnostic features of PCNSL patients at CHRU de Tours from 2017 to 2023. It focuses on MRI feature, ophthalmological examination, brain biopsy results and biomarker findings in CSF and vitreous humor.

65 adult patients with a confirmed PCNSL were included. Brain biopsy, performed in 34 cases (52%), remained the gold standard. Cytological confirmation, including immunophenotyping, was decisive in 17% of cases with vitreous samples and 14% with cerebrospinal fluid (CSF) samples. Elevated interleukin levels alone guided treatment in 6% of patients with vitreous samples and 5% with CSF samples. Lastly, 6% of patients, without definitive biological markers, were treated based on clinical presentation and characteristic MRI features after ruling out major differential diagnoses.

PCNSL diagnosis can be achieved through various methods. Indirect biological markers like interleukin 6 and 10, while helpful, remain supplementary diagnostic tools. A standardized diagnostic protocol could enhance rapid diagnosis and timely treatment, which is crucial for improving therapeutic outcomes.