In the univariate analysis of the baseline characteristics, the following parameters were associated with multiple BM: negative PR (progesterone receptor) status in BM (p = 0.016), infratentorial tumor localization (p = 0.002), hepatic metastasis (p = 0.020) and positive human epidermal growth factor receptor 2 (HER2) status in BC (p = 0.012, see Supplementary Table 1). The gene discussed is ERBB2; the disease is neoplasm.