Epidermal growth factor receptor (EGFR) mutations, such as deletions in exon 19 and point mutations in exon 21, are considered the most reliable predictive factors of outcome after treatment of non-small cell lung cancer (NSCLC) with EGFR tyrosine kinase inhibitors (EGFR-TKIs). This evidence concerns the gene EGFR and non-small cell lung carcinoma.