Among 14 cancer classification marker genes corresponding to immunostaining status, nine genes were found to show significant differences in gene expression among Di Palma classifications, suggesting that immunostaining appropriately reflects the gene expression profiles and that each subtype based on Di Palma classification (“HER2-positive”, “Luminal-AR”, and “Basal-like”), has a different gene expression profile. The gene discussed is ERBB2; the disease is cancer.