Subgroup analysis revealed significant higher APRIL CSF levels in active CNSL (8.0 [1.32–28.82]) compared to patients with primary brain tumors (PBT, 2.55 [0–8.71] ng/ml, P < .001), metastatic brain tumors (MBT, 4.70 [2.00–17.01] ng/ml, P < .01), autoimmune-inflammatory diseases (AID, 2.61 [0.36–6.35] ng/ml, P < .001), and neuroinfectious diseases (NID, 3.44 [0.93–3.48] ng/ml, P < .01) (Fig. 1b). This evidence concerns the gene TNFSF13 and brain neoplasm.