CD34 and central nervous system cancer: As shown in Figure 3A, using a random effects model, a significant association between CD34 overexpression and higher WHO grades was revealed by the SMDs (SMD -1.503, 95% CI -1.685 to -1.321; P = 0.000), which indicated that there was higher CD34 expression in the postoperative glioma tissues than normal cerebral tissues and this could be used to predict gliomas of high grades.