EGFR and adenocarcinoma: 10–15% of Caucasians and up to 50% of Asians with lung adenocarcinoma have an activating mutation in the EGFR gene[5], and approximately 93% of adenocarcinomas demonstrate EGFR expression[6], with 40–80% of adenocarcinomas exhibiting overexpression of EGFR[5, 7].