BACKGROUND
The clinical significance of progesterone receptor (PgR) expression in estrogen receptor-negative (ER-) breast cancer is controversial. Herein, we systemically investigate the clinicopathologic features, molecular essence, and endocrine responsiveness of ER-/PgR+/HER2- phenotype.
METHODS
Four study cohorts were included. The first and second cohorts were from the Surveillance, Epid...