Poor prognosis of single hormone receptor- positive breast cancer: similar outcome as triple-negative breast cancer

We have identified clinically and biologically distinct features of single HR+ tumors (ER-PR+ and ER + PR-) through comparison with both ER + PR+ and ER-PR- tumors. These differences were only significant in HER2- tumors, not in HER2+ tumors. Single HR+ tumors without HER2 overexpression (ER + PR-HER2- or ER-PR + HER2-) were associated with poorer survival than ER + PR + HER2- tumors, and had comparable poor survival to ER-PR-HER2- tumors (triple-negative breast cancer).