Besides validating the prognostic role of Ki67 expression in tumor samples in 70 PM patients from two different centers with detailed clinical characteristics, here we suggest for the first time Ki67 as a biomarker to predict the patient’s benefit from lung-sparing surgery within multimodality therapy in epithelioid mesothelioma. The gene discussed is MKI67; the disease is malignant epithelioid mesothelioma.