EGFR and non-small cell lung carcinoma: Systematic genetic and histologic analyses of tumor biopsy specimens from 37 patients with drug-resistant EGFR mutation-positive NSCLC were performed to determine mechanisms of acquired resistance and found that all tumors retained their pretreatment activating EGFR mutations and many acquired other resistance mechanisms, including T790M or MET gene amplification (Fig.2) 53.