PGR and breast cancer: The concordance in biomarker expression was then evaluated between the primary BC and the LNM, thereby showing concordance rates of 98.9% for ER (ER-positive: 90.4%; ER-negative: 8.5%), 95.8% for HER2 (HER2-positive: 6.4%; HER2-negative: 89.4%), 89.4% for PR (PR-positive: 71.3%; PR-negative: 18.1%), and 72.3% for Ki67 (Ki-67 high: 31.9%; Ki-67 low: 40.4%; Table 3).