ERBB2 and small cell lung carcinoma: The activation of bypass receptors, including mesenchymal–epithelial transition factor (MET) amplification, human epidermal growth factor receptor 2 (HER2) activation, and fibroblast growth factor receptor (FGFR) amplification; the transformation of phenotype, including epithelial–mesenchymal transition (EMT); and transformation to small cell lung cancer play an essential role in the tolerance of EGFR-TKI (Kim et al., 2015; Westover et al., 2018).