Endoscopic appearance of dysplasia and cancer in inflammatory bowel disease.

Dysplastic alteration of mucosa may occur in flat or raised mucosal lesions. Over 95% of dysplastic foci occur in flat mucosa. Flat dysplasia is occasionally visible macroscopically as areas of discolouration, velvety-villous appearance, or peculiar fine nodular thickening. The prevalence of macroscopically visible flat dysplasia is unknown. Raised dysplasia or DALM (dysplasia associated lesion or mass) occurs in less than 5% of patients with dysplasia. DALMs are polypoid structures of firm consistency, discoloured mucosa and irregular nodularity. DALMs cannot be distinguished endoscopically from early malignancy. The presence of DALMs has an ominous significance.