We performed immunohistochemical (IHC) analysis in 22 cases of HER2+ BC and confirmed that tumors from patients remaining disease-free following trastuzumab treatment showed an increased number of intra-tumoral CD45 + immune cells (leukocytes) compared to tumors from relapsing patients (Fig. 1a, Supplementary Fig. 1a). Here, PTPRC is linked to breast cancer.