ERBB2 and breast cancer: In the multivariate analysis, the presence of hepatic metastases (adjusted odds ratio [aOR] 5.86, 95% confidence interval [CI] 1.34–25.61, p = 0.019), infratentorial location of resected BM (aOR 3.35, 95% CI 1.03–10.83, p = 0.044), and a positive HER2 RS in the primary BC (aOR 3.93, 95% CI 1.23–12.53, p = 0.021) were more common in the cohort with multiple BM (see Supplementary Table 2).