She was a 75-year-old female patient with pre-treated metastatic cholangiocarcinoma harboring an ERBB2 amplification (Copy number; CN = 114) and treated with dual human epidermal growth factor receptor 2 (HER2) blockage therapy (trastuzumab and pertuzumab), and a good clinical response was observed for 9 months until the appearance of pleural effusion. Here, ERBB2 is linked to Pleural effusion.