Since the sample type may be an important confounding factor for EGFR gene testing, we separately investigated the incidence of EGFR gene mutation in the tissues and plasma. It was noted that EGFR gene mutation rate in the tissues was 53.40% (361/676), and the EGFR gene mutation rate in the plasma and pleural effusion cells was 25.00% (47/188). This evidence concerns the gene EGFR and Pleural effusion.