Amplification of ERBB2 is one of the mechanisms of acquired resistance to first-generation EGFR-TKI in EGFR-mutant NSCLC tumors that lack the EGFR T790M secondary mutation.[4] In the current case, the amplification refractory mutation system test for the primary tumor demonstrated the presence of TKI sensitive mutation EGFR exon 19 deletion and it indeed showed good response to Gefitinib. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.