Compared with the other two groups, the older group had fewer occurrences of brain-only metastatic disease and liver-only metastatic disease in luminal A subtype (0.03% and 0.07%, respectively), luminal B subtype (0.33% and 0%, respectively), HER2-enriched subtype (0% and 0%, respectively), and triple-negative subtype (0.38% and 0.19%, respectively) (P<0.001) (Fig. 2). Here, ERBB2 is linked to metastatic neoplasm.