Then, we performed the partitioning around medoid (PAM) clustering analysis and classified the HR+/HER2– breast cancers into 2 subtypes, namely immune-hot (IHot, characterized by a relatively high immune cell and low stromal cell infiltration level) and immune-cold (ICold, characterized by a converse landscape) (Figure 1B and Supplemental Figure 1B). This evidence concerns the gene ERBB2 and breast cancer.