DAPK1 and primary central nervous system lymphoma: Our data are in line with Chu et al. and Gonzales-Gomez et al. [5,8] analyzing the DNA methylation of CDKN2B, DAPK1, GSTP1, MGMT, MLH1, RARB, THBS1, TIMP2, and TIMP3 in PCNSL by MSP (Additional file 8) further supporting the validity of our analysis.