PGR and breast cancer: Of note, PFOA was associated with the occurrence of estrogen receptor (ER)-, progesterone receptor (PR)-, and human epidermal growth factor receptor 2 (HER2)-positive breast cancer (ORER+  = 1.47, 95% CI: 1.19, 1.80; ORPR+  = 1.36, 95% CI: 1.09, 1.69; ORHER2 = 1.62, 95% CI: 1.19, 2.21).