ERBB2 and gastric cancer: Great benefit has been seen in breast cancer or gastric cancer patients treated with Trastuzumab, a monoclonal antibody against HER2.12 Several HER2‐tyrosine kinase inhibitors (TKIs) have also been found to be effective in NSCLC cell lines with HER2 mutation.8, 13, 14 However, response to HER2‐TKIs has been reported to be unsatisfactory in HER2 mutated NSCLC patients.9, 15, 16, 17