FACS analyses of cells released from the biopsy revealed that the mean percentage and number of CD45+ leukocytes was >10 times higher in samples from patients subsequently histologically diagnosed as PCNSL (n = 8, M = 31.3%, SEM = 9.8%; M = 366,094 cells, SEM = 94,908 cells) than in glioblastoma patients (n = 8, M = 3.1%, SEM = 1.7%; M = 24,353 cells, SEM = 5758 cells) (Fig. 1B). This evidence concerns the gene PTPRC and primary central nervous system lymphoma.