EGFR and non-small cell lung carcinoma: Intratumoral heterogeneity in epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC), which has been found to range from 13.9 to 27%, explains the mixed-response phenomenon and results in acquired resistance to tyrosine kinase inhibitors (EGFR-TKIs) [1].