EGFR and small cell carcinoma: Studies have identified different mechanisms of acquired EGFR-TKI resistance, including a second-site EGFR T790M mutation [12, 13], MET amplification [14, 15], PIK3CA mutations [16], FGFR1 activation [17], epithelial-to-mesenchymal transitions and conversion to small cell carcinoma [16, 18-19].