ERBB2 and breast cancer: A total of 2146 stage IV patients (63.41%) were diagnosed with HR+/HER2- breast cancer, 672 stage IV patients (19.86%) were diagnosed with HR+/HER2+ breast cancer, 316 stage IV patients (9.34%) were diagnosed with HR−/HER2- breast cancer, and 250 stage IV patients (7.39%) were diagnosed with HR−/HER2+ breast cancer.