Mutation of the EGFR proto-oncogene is found in 10% to 20% of lung carcinomas (mostly adenocarcinomas) and nearly 90% of lung cancer-specific EGFR mutations comprise a leucine-to-arginine substitution at position 858 (L858R) and deletion mutations in exon 19 (delE746-A750) [7-10]. The gene discussed is EGFR; the disease is lung cancer.