- Histologically documented breast cancer (either primary or metastatic site) that is ER (estrogen receptor)-negative, PgR (progesterone receptor)-negative ( <10% tumor staining by immunohistochemistry [IHC]) and HER2 (human epidermal growth factor 2) non-overexpressing by IHC (0,1+) or, IHC 2+ and FISH (fluorescence In situ hybridization) negative.