Comparing the stratified variables between 51 postoperative metastatic patients with BM and 163 postoperative metastatic patients without BM, the result of univariate analysis showed that age ≤ 40 years and first metastatic site with lung metastasis were significantly associated with the risk of BM in patients with HER2-positive BC (Table 1). The gene discussed is ERBB2; the disease is breast cancer.