ERBB2 and breast cancer: Number of positive nodes, and size and chest wall involvement of the breast tumors exhibited similar significance for breast cancer-specific mortality in the population (p < 0.0001 each), and all-cause mortality in hormone receptor (HR)-positive/HER2-negative (HR+/HER2–), HR+/HER2+, HR–/HER2+ and triple-negative metastatic breast cancer subtypes.