PTGS2 and esophageal squamous cell carcinoma: Clinico-pathological and immuno-histochemical analysis was carried out in ESCC patients to evaluate impact of risk factors in ESCC and COX-2 expression in different stages of cancer development; normal squamous epithelium of 40 patients, dysplastic tissue (CIS) of 19 patients and invasive ESCC of 69 corresponding patients.