MKI67 and metastatic malignant neoplasm in the lymph nodes: Twenty-three studies comprising 2994 cases were used for meta-analysis of Ki-67 expression and lymph node metastasis, and the pooled OR indicated that a high Ki-67 level was significantly correlated with lymph node metastasis positive (OR = 1.653, 95%CIs: 1.285–2.127, Z = 3.91, P < 0.0001; I2 = 46.70%, P = 0.008, Additional file 3: Figure S3B).