PGR and breast cancer: ,115 Triple-negative BC (TNBC: HR-/HER2-) is an aggressive form characterized by the absence of estrogen receptors (ERs), progesterone receptors (PRs), and HER2 expression, and shows the lowest 5-year survival rate (78%) and worse long-term prognosis compared to hormone receptor-positive (HR+) counterparts, as we reviewed recently.116