This study aimed to investigate intratumor heterogeneity in HER2-positive breast cancer cases by comparison with luminal breast cancer (HR-positive/HER2-negative) using an integrated scRNA-seq cohort because we aimed to focus on the comparison between the luminal and HER2 subtypes to investigate the relationship between ER and HER2 status [8]. The gene discussed is ERBB2; the disease is breast cancer.