ERBB2 and breast cancer: Furthermore, the higher risk of breast cancer death in low-grade HR+/HER2+ disease and lower risk of death in high-grade HR+/HER2+ disease than HR+/HER2- disease could result from women with high-grade HR+/HER2+ disease being more likely than those with low-grade HR+/HER2+ disease to receive adjuvant trastuzumab, as suggested by recent studies on patterns of care [47-49].