In-frame exon 20ins represent 5–10% of all EGFR-mutations in NSCLC and occur more frequently between codon 767 and 775 encoding the C-helix of EGFR-TK domain (A767 to C775) that regulates the binding of both ATP and EGFR-TKIs. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.