EGFR and non-small cell lung carcinoma: Several types of activating mutations are known to occur in EGFR in NSCLC: Class I - exon 19 in-frame deletions (44% of all EGFR mutations), Class II - single amino acid changes (L858R 41%, G719 4%, other missense mutations 6%), Class III - exon 20 in-frame duplication/insertions (5%).