The results of the immunohistochemical analysis evaluating the expression status of the ER, PgR, and Ki-67 antigens, FISH detecting HER2 amplification, and the histological features in conventional tissue sections stained with hematoxylin-eosin. Upper rows: A case of invasive ductal carcinoma classified into the luminal A subtype. The ER was expressed in 100% of the tumor cells, and the PgR was expressed in 90% of them. No HER2 amplification was detected (green and red spots indicate chromosome 17 centromeres and HER2). The Ki-67 antigen was expressed in 1% of the cells in this tumor (Ki-67 index = 1%). Lower rows: A medullary carcinoma was classified into the basal-like subtype. The ER and PgR are apparently not expressed in any of the tumor cells. No HER2 amplification was detected. The Ki-67 antigen was expressed in 70% of the tumor cells (Ki-67 index = 70%).