A trend toward positive correlation was found between a high Ki-67 level and larger tumor size in 12 studies based on 1707 lung cancer patients, with a pooled OR of 1.436 (95%CIs:1.127~ 1.290,, Z = 2.93, P = 0.003; I2 = 0.00%, P = 0.876, Additional file 3: Figure S3A). The gene discussed is MKI67; the disease is lung cancer.