Li Z, Li F, Pan C, et al. - In histological subtypes of lung adenocarcinoma, the present study was conducted to evaluate Ki-67 expression and its prognostic significance. There were 1,028 invasive lung adenocarcinoma (LUAD) patients who were treated surgically between January 2012 and April 2020 retrospectively analyzed. Researchers evaluated relationships between Ki-67 expression and histological subtypes of LUAD and other clinicopathological features. The log-rank test and univariate/multivariate Cox proportional hazards regression analyses were applied to evaluate the prognostic role of Ki-67 in LUAD subtypes. The highest expression level of Ki-67 was seen in solid-predominant adenocarcinoma, followed by micropapillary, papillary, acinar, and lepidic-predominant adenocarcinoma. Higher Ki-67 expression was also seen in tumors with solid or micropapillary components vs those without. Outcomes suggested that Ki-67 expression level and tumor size contributed to the survival differences between LUAD histological subtypes.