ERBB2 and breast cancer: Oestrogen‐receptor (ER) status was known for 6,994 (72.5% of invasive and 43.5% of in situ) breast cancer patients; ER, progesterone‐receptor (PR) and HER2‐status was available for 3,425 (37.2% invasive, 13.9% in situ) breast cancer patients.