EGFR and Pleural effusion: Of the 108 effusion samples, 103 (95.4%) were pleural effusions and 5 (4.6%) were ascites, and 12, 87, and 9 samples (11.1%, 80.6%, and 8.3%) were obtained before EGFR–TKI treatment, after 1 EGFR–TKI treatment session, and after 2 or more EGFR–TKI treatment failures, respectively.