PLK1 and metastatic malignant neoplasm in the lymph nodes: We observed that PLK1 protein’s high expression positively correlated with differentiated degree (high or middle compared with low, P<0.001), clinical stage (I–II compared with III–IV, P<0.001), tumor size (T1–T2 compared with T3–T4, P<0.001), lymph node metastasis (N1 compared with N2–N3, P<0.001), and distant metastasis (M0 compared with M1, P=0.002).