The results from 11 studies enrolling 1731 lung cancer patients showed that an elevated Ki-67 level was associated with poor differentiation, with a pooled OR of 1.993 (95%CIs:1.262–3.146, Z = 2.96, P = 0.003; I2 = 66.30%, P = 0.001, Additional file 2: Figure S2B). The gene discussed is MKI67; the disease is lung carcinoma.