The results showed that TNF-α (RR = 1.123, 95% CI 1.052–1.199; P < 0.001), a number of lymph node metastases of 4–9 (RR = 2.763, 95% CI 1.512–5.048; P = 0.001), and a number of lymph nodes ≥ 10 (RR = 3.088, 95% CI 1.756–5.432; P < 0.001) were risk factors for distant metastasis after BC (Table 6). The gene discussed is TNF; the disease is breast cancer.