The common ARs include: (i) secondary mutations to EGFR, such as T790M mutation, C797S mutation [5]; (ii) activation of alternative pathways, such as MET amplification [6], ERBB2 amplification [7]; (iii) activation of downstream targets, for instance, RAS-MAPK pathway signaling [8], PIK3CA mutations [9]; (iv) histologic transformation, for example, small-cell lung cancer (SCLC) transformation [10]; (v) others: fibroblast growth factor receptor (FGFR) amplification, cell cycle gene alterations [8]. The gene discussed is PIK3CA; the disease is small cell lung carcinoma.