The epidermal growth factor (EGF) receptor is a 170 kDa transmembrane tyrosine kinase that belongs to the HER/ErbB protein family. Research studies have shown that somatic mutations in the tyrosine kinase domain of EGF receptor (EGFR) are present in a subset of lung adenocarinomas that respond to EGFR inhibitors, such as gefinitib and erlotinib. Two types of mutations account for approximately 90% of mutated cases: a specific point mutation, L858R, that occurs in exon 21 and short in-frame deletions in exon 19 . The most frequent exon 19 deletion is E746-A750, accounting for 90% of lesions at this site, although some rare variants occur.
