There is no consensus on the definition of HER2 protein overexpression in lung cancer, but clinical studies frequently use a score of 2+ (“weak to moderate complete membrane staining observed in >10% of tumor cells”) or 3+ (“circumferential membrane staining that is complete, intense and in >10% of tumor cells”) as per the American Society of Clinical Oncology/College of American Pathologists breast cancer guidelines [11]. This evidence concerns the gene ERBB2 and breast carcinoma.