MKI67 and cancer: Some studies suggest that tumor cells with high PD-L1 expression exhibit greater proliferative activity, as indicated by higher Ki-67 indices,11 and may exhibit epithelial-to-mesenchymal transition and cancer stem cell-like characteristics, conferring stronger invasiveness and facilitating metastasis to the pleural cavity, leading to malignant effusion.12 This study utilized an objective, molecular-based indicator to evaluate the impact of PD-L1 expression on the biological behavior of LUAD.