Prognostic significance of the progesterone receptor status in Ki67-high and -low Luminal B-like HER2-negative breast cancers

Background Breast cancer is a heterogeneous disease, and immunohistochemical evaluation is a surrogate marker that is widely used in clinical settings to identify the intrinsic subtypes. The definition of the Luminal B-like breast cancer was changed at the 2013 St. Gallen meeting; therefore, we investigated the clinicopathological features of the new Luminal B-like breast cancer categorized in the latest definition. We also compared the conventional PgR-high Luminal B-like breast cancer with the conventional PgR-low or -negative Luminal B-like breast cancer.