33 reported that COX‐2 expression was correlated with tumor grade. Pooled data from six studies with 294 cases revealed that COX‐2 expression was positively linked to tumor grade (OR = 4.81) and clinical stage (OR = 4.89). Dickens et al. 46 found no significant association between COX‐2 expression and metastatic status. Rodriguez 2008 et al. also reported that no correlation existed between COX‐2 expression and metastasis in osteosarcoma 32. Conversely, Urakawa et al. 31 reported that the expression of COX‐2 was significantly related to the metastatic status of osteosarcoma. The gene discussed is PTGS2; the disease is neoplasm.