EGFR and adenocarcinoma: It was demonstrated in our study that frequency of EGFR mutation in well-differentiated adenocarcinoma was significantly higher than that in poorly-differentiated adenocarcinoma, while PIONEER study showed that the mutational rate of EGFR was significantly higher in invasive adenocarcinoma than in bronchioloalveolar carcinoma, which is currently called pulmonary adenocarcinoma in situ.