We examined BC patient peripheral blood mononuclear cells (PBMCs), tumor-negative tumor-draining lymph nodes (T– LNs), tumor-positive tumor-draining lymph nodes (T+ LNs), primary tumors, and noncancerous breast tissue (NCBT) by flow cytometry for the presence of CD8+ T cells expressing T cell exhaustion markers PD-1 and CD39 (Figure 1A; gating strategy in Supplemental Figure 1; supplemental material available online with this article; https://doi.org/10.1172/jci.insight.153963DS1). Here, CD8A is linked to neoplasm.