PTGS2 and esophageal squamous cell carcinoma: Interestingly, COX-2 expression in ESCC of HNC patients shows several similarities to that in ESCC patients without HNC: low homogeneous COX-2 expression in normal epithelium, increasing expression during carcinogenesis, homogeneous COX-2 distribution in all dysplasias, and intra- and intertumoural heterogeneity of COX-2 expression in carcinoma tissues (Zimmermann et al, 1999; Ratnasinghe et al, 1999; Shamma et al, 2000).