[Morphologic features of ulcerative colitis].
Ulcerative colitis(UC) is an ulcero inflammatory disorder of unknown etiology affecting only the mucosa and submucosa of colon and, with Crohn's disease, is included in the term idiopathic inflammatory bowel disease. The macroscopic and microscopic features vary according to the stage of the disease process, and an acute phase and a chronic or resolving phase can be recognized. The main differential diagnosis of UC is with colorectal Crohn's disease. The most feared long-term complication of UC is cancer. The progression of UC to carcinoma is closely associated with dysplasia arising in multiple sites. The dysplastic changes should be distinguished from the epithelial changes resulting from regenerative atypia, and the evaluation of these changes is difficult. P53 immunohistochemical staining is helpful in confirming the presence of dysplasia. Molecular events in colorectal carcinogenesis of UC may be somewhat different from those of so-called adenoma-carcinoma sequence.