PTGS2 and metastatic malignant neoplasm in the lymph nodes: In Cox regression for OS including patients' age, gender, lymph node metastasis, histological differentiation, invasion depth, stage, COX-2 expression, VEGF-C expression, and peritumoral LVD, only age (P = 0.015, RR = 2.891, 95% confidence interval, 1.228-6.805), COX-2 expression (P = 0.021, RR = 3.244, 95% confidence interval, 1.192-8.828) and peritumoral LVD (P = 0.001, RR = 4.292, 95% confidence interval, 1.778-10.360) remained as independent prognostic factors.