Nine factors were included in the nomogram: the dimension of the largest BM, the number of CNS metastases, KPS, the age at the detection of BM, ECM (yes vs. no), the BC stage (I, II, III, IV) and expression of the estrogen receptor (ER) (positive vs. negative), progesterone receptor (PR) (positive vs. negative) and HER2 (positive vs. negative). The gene discussed is ERBB2; the disease is breast cancer.