PDPN and metastatic malignant neoplasm in the lymph nodes: However, PDPN has no correlations with TNM stage (pooled OR = 1.58, 95% CI 0.53–4.69, P = 0.41, random effect) (Fig. 2a), lymphatic invasion (pooled OR = -0.04, 95% CI -0.23-0.14, P = 0.64, random effect) (Fig. 2b), vascular invasion (pooled OR = 0.95, 95% CI 0.63–1.42, P = 0.79, fixed effect) (Fig. 2c), pleural metastasis (pooled OR = 3.29, 95% CI 0.96–11.33, P = 0.06, random effect) (Fig. 2d), lymph node metastasis (pooled OR = -0.08, 95% CI -0.29-0.14, P = 0.49, random effect) (Fig. 2e), sex (pooled OR = 1.15, 95% CI 0.72–1.86, P = 0.56, fixed effect) (Fig. 2f).