| [ Summary ] |
Dysplastic lesions, other than carcinomas, occurring in patients with ulcerative colitis consist of classic dysplasia-associated lesions or masses (DALMs), polypoid dysplasia (adenoma-like DALM), flat dysplasia endoscopically invisible, adenoma-like masses (ALMs) without flat dysplasia, and sporadic-type adenoma. The former two types of lesions require colectomies but the same treatment is not always recommended for the latter three lesions. Diagnostic problems rarely occur in classic DALMs, because they display irregular protuberant or villous plaque with and ill-defined edges and the gross appearance is distinct from that of sporadic-type adenomas. Although reliable differentiation between polypoid dysplasia and sporadic-type adenoma is often difficult, the former can be diagnosed when younger patients (< 50 yr) with long disease duration (> 10 yr) display adjacent flat dysplasia, an admixture of normal and dysplastic epithelium at the surface of the polyp, a high degree of lamina propria mixed inflammation, and the combination of strong p53 expression and absent or weak β-catenin expression. The reverse features suggest sporadic-type adenoma, and ALM is temporally used for the indeterminate lesions. This review also refers to interobserver variability in grading systems for dysplasia and discusses helpful immunohistochemical findings associated with p53 and Ki67. |