- Histologically confirmed triple negative breast cancer (TNBC), defined as negative immunohistochemical staining for estrogen and progesterone receptors (≤5% of nuclei positive by IHC) and receptor tyrosine-protein kinase erbB-2 (HER2) negative (IHC 0-1+ or HER2-neu negative according to American Society of Clinical Oncology; College of American Pathologists (ASCO-CAP) HER2 Test Guideline Recommendations)