Biology and prognosis of HER2-negative breast cancer with low-ER and PgR-expressions.

e12020Background: Expression of the estrogen (ER) and progesterone receptor (PgR) is still clinically important in predicting prognosis and determining therapeutic strategies in breast cancer. According to the ASCO and CAP guidelines tumors with ≥1% positively staining cells should be considered ER/PgR positive. The clinical significance of low-ER/PgR-staining (1-9%) tumors were analyzed to investigate the biology and prognosis. Methods: This study examined 3193 consecutive HER2 negative invasive breast cancer cases. Clinicopathological characteristics and prognosis of hormone receptor (HR)-negative (<1%), low-HR-staining (1-9%) tumors and positive (≥ 10%) tumors were compared. The median follow-up period was 75 months. Results: The following is the number of patients in each of the tumor categories: 466 ER cases (14.6%) and 775 PgR cases (24.2%) in the <1% group; 68 ER cases (2.1%) and 218 PgR cases (6.8%) in the 1-9% group; and 2559 ER cases and 2200 PgR cases in the ≥ 10% group. The age groups were; yo...