ERBB2 and breast carcinoma: Previous studies suggested that overexpression of HER2 is a frequent molecular abnormality in primary breast cancer and primary gastric cancer.[21] We are aware of that more studies are required to better understand how pyrotinib acts on HER2-positive breast cancer and HER2-positive gastric cancer.[22] Moreover, a randomized clinical trial would be important to demonstrate efficacy in HER2-positive gastric cancer.