In the analysis of the correlation between serum MSLN expression and clinicopathological imaging characteristics of lung cancer patients with BM, it was found that the serum level of MSLN was significantly correlated with smoking history, BM maximum diameter, meningeal metastasis, number of primary lung lesions, pleural effusion, and epidermal growth factor receptor (EGFR) mutation status (Table S4). The gene discussed is MSLN; the disease is Pleural effusion.