Several groups reported that a substantial percentage of NSCLC tumors getting objective response when treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) harbor activating somatic mutation in the EGRF gene including in frame deletion or amino-acid substitution clustered around ATP- binding pocket of EGFR tyrosine kinase domain (in exons 18, 19, and 21) [13–16]. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.