PLK1 and metastatic malignant neoplasm in the lymph nodes: As shown in Table 3, the increased expression of PLK1 was positively associated with lymph node metastasis (OR: 1.78, 95% CI: 1.13–2.80, P=0.013, random effect model) and advanced TNM stage (OR: 1.48, 95% CI: 1.02–2.15, P=0.038, random effect model).