ERBB2 and non-small cell lung carcinoma: Subsequently, its usage has been extended to HER2-low (IHC 1+ or IHC 2+/ISH-) breast cancer5, HER2-positive gastric or gastroesophageal (GEJ) adenocarcinoma6, and unresectable or metastatic non-small cell lung cancer with HER2 mutation7.