TNFSF13B and leptomeningeal metastasis: BAFF CSF levels were elevated above the threshold of 299 pg/ml (as calculated in ROC analysis, Fig. 2) in four patients with focal brain lesions other than CNSL: one patient with lung adenocarcinoma and concomitant meningeal carcinomatosis (880 pg/ml) and one patient with glioblastoma multiforme and concomitant CSF inflammatory syndrome (351 pg/ml); both of them also showed high APRIL CSF levels.