ERBB2 and small cell lung carcinoma: T790M represents ~ 60% of first‐ and second‐generation TKI resistance mechanism; MET amplification, HER2 amplification, PIK3CA mutation, and BRAF mutations collectively account for ~ 20%; histological transformation from NSCLC to small cell lung cancer accounts for ~ 5%; the remaining mechanisms remain unknown (Faehling et al., 2017; Lim et al., 2018; Lin et al., 2014).