ERBB2 and lung adenocarcinoma: Because HER2 overexpression (IHC 2+ and 3+) is observed in 15–30% of lung adenocarcinoma28–31 and HER2 3+ and/or amplification is observed in 2–6% of lung adenocarcinoma,28–32 the pre-EGFR TKI treatment tumour samples were analysed for HER2 expression as well.