Hormone Receptor and Human Epidermal Growth Factor Receptor 2 Detection in Invasive Breast Carcinoma: A Retrospective Study of 12,467 Patients From 19 Chinese Representative Clinical Centers

We evaluated the current status of hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) detection in invasive breast carcinoma (IBC) in various laboratories across China.The Breast Pathology Study Group of the Chinese Society of Pathologists collected HR and HER2 data from 12,467 IBC cases from 19 representative clinical centers in China. The data from every center were compared with the pooled data from the other centers.The assessment of HR status showed that the overall positive estrogen receptor (ER) and progesterone receptor (PR) rates were 71.7% and 63.7% (range, 60.9%-87.9% and 43.9%-84.8%), respectively. The ER results in 3 centers and the PR results in 6 centers were outside the 99.5% confidence interval and were considered to be outliers (P < .0005). Of the 12,467 cases, 62.4% were ER+/PR+, 9.3% were ER+/PR-, 1.3% were ER-/PR+, and 27.0% were ER-/PR-. The assessment of HER2 status showed that the overall positive rate of HER2 (with a definition of immunohistochemistry [IHC] 3+ or IHC2+/ in situ hybridization-positive) was 24.7% (range, 13.7%-35.7%) in each center. Three centers were outside the 99.5% confidence interval and were considered to be outliers (P < .0005). The proportion of HER2 IHC3+ was 21.1%. The positive rates of HER2 gene amplification in IHC 0/1+, 2+, 3+ cases were 2.0%, 17.6%, and 85.9%, respectively.As the largest study of HR and HER2 status in Chinese patients with IBC, the data from the present study have indicated that the overall rates of HR and HER2 were comparable to those reported in previous studies. However, the rates varied among the laboratories. Individual centers had not met the target values, and they need to improve the detection.