Previous reports have identified the role of tumor infiltrating lymphocytes in predicting responses to chemotherapy in triple negative and HER2 positive breast cancers, but the role in ER + disease has been less well-defined.35,36 This suggests that measuring pnSTING may be able to add granularity to the activation state of the immune infiltrate in ER + disease, therefore identifying tumors with immune restriction and poor clinical outcomes to standard of care, suggesting alternative treatment options should be considered. Here, ESR1 is linked to breast carcinoma.