For the VSIG4 peptide GSDPVTIFLR, a sensitivity of 71.4% and specificity of 90.0% can be estimated at a cut-off of 36.2 fmol/μg protein and TAAQNLYEK (APOC2) can discriminate PCNSL from glioma patients at a cut-off of 8.3 fmol/μg with a sensitivity and specificity of 84.6% and 77.7%, respectively. Here, APOC2 is linked to central nervous system cancer.