ABSTRACT
Patients with long-standing history of ulcerative colitis have an increased risk of developing colitis-associated colorectal cancer.The risk factors include longer duration of colitis,greater anatomic extent of colitis,degree of inflammation of the bowel,family history of colorectal callcer,the presence of primary sclerosing cholangitis.etc.The two kinds of molecular pathogenesis that contribute to colon carcinogenesis are chromosomal instability and microsatellite instability.In order to reduce cancer morbidity,colonescopic surveillance and chemoprevention should be carried out in patients with ulcerative colitis especially in those high risk patients.New endoscopic techniques increase the sensitivity and shed a new light on tumor surveillance.