MPE is a common complication in NSCLC and its collection is easier, safer, and more repeatable than the collection of MPTTs.[17], [18] Although many studies have been done to show that MPEs are good for detection of EGFR mutations,[9], [12], [19], [20] the MPEs were not matched with corresponding MPTTs, which compromised the credibility of the results. This evidence concerns the gene EGFR and non-small cell lung carcinoma.