Factors predisposing to colorectal cancer in UC patients consist of pancolitis, duration of disease, active disease and its severity. Early UC onset is another independent risk factor. Beside these factors, dysplasia represents the precancerous lesion from which colorectal cancer subsequently arise (Morson, 1962; Morson & Pang, 1967). In fact, 70% of patients with colorectal cancer on UC have dysplasia on colorectal mucosa (Taylor et al., 1992; Connell et al., 1994). Severe dysplasia is reported to develop colorectal cancer in 45% of cases, whereas there are too few data in literature to do a similar valuation for mild-moderate dysplasia (Collins.
