Microscopic features of ulcerative colitis. Microscopically, these changes of chronic active colitis are diffuse and uniform in distribution: that is, every biopsy fragment from the diseased colon shows a similar degree of injury and inflammation. Rarely, pyloric gland metaplasia may also be seen in UC ( Figure 2C). While Paneth cells are a normal component of the right colon, their presence in the left colon is a metaplastic process, due to chronic crypt epithelial injury ( Figure 2C). Basal lymphoplasmacytosis refers to the presence of a lymphoplasmacytic infiltrate between crypt bases and the muscularis mucosae ( Figure 2B). In normal mucosa, the crypts are uniformly spaced, arranged perpendicular to the muscularis mucosae, and the crypt bases contact the upper edge of the muscularis mucosae. presence of space between the bottom of the crypts and the upper edge of the muscularis mucosae) and branching of the crypts ( Figures 2A and B). Architectural distortion is represented by shortening of the crypts (i.e. Chronicity is defined by crypt architectural distortion, basal lymphoplasmacytosis, or Paneth cell metaplasia in the left colon. Activity is defined as the presence of neutrophil-mediated epithelial injury, which may take the form of neutrophils infiltrating crypt epithelium (cryptitis), collections of neutrophils within crypt lumens (crypt abscesses), or by infiltration of surface epithelium with or without mucosal ulceration. In untreated disease, UC usually exhibits a histological pattern of chronic active colitis, which refers to the presence of active inflammation accompanied by features of chronic mucosal injury. The surveillance interval and treatment options for UC patients with dysplasia are reviewed in detail. The natural history of low-grade dysplasia (LGD) is more controversial: while multifocal LGD, particularly if detected at the time of initial endoscopic examination, is treated with colectomy, unifocal flat LGD detected during surveillance may be managed by close follow-up with increased surveillance. UC patients with DALM or flat high-grade dysplasia should be treated by colectomy because of the high probability of adenocarcinoma. Recent data suggest that such lesions may be treated adequately by polypectomy in the absence of flat dysplasia in the patient. Isolated polypoid dysplastic lesions are considered to be sporadic adenoma if occurring outside areas of histologically proven colitis, or adenoma-like dysplasia if occurring in the diseased segment. Accurate interpretation and classification of dysplasia in colon biopsy from UC patients as sporadic adenoma or UC-related dysplasia requires clinical and endoscopic correlation. Colon biopsy from UC patients should always be evaluated for dysplasia based on cytological and architectural abnormalities. Patients with UC are at risk for the development of dysplasia and carcinoma optimal outcomes in UC surveillance programs require familiarity with the diagnostic criteria and challenges relating to UC-associated dysplasia and malignancy. Indeterminate colitis should only be used in colectomy specimens as a provisional pathological diagnosis. Loosely formed microgranulomas, with pale foamy histiocytes adjacent to a damaged crypt or eroded surface, should not be interpreted as evidence of Crohn’s disease. These atypical pathological presentations include rectal sparing and patchiness of disease at initial presentation of UC in pediatric patients or in the setting of medically treated UC, cecal or ascending colon inflammation in left-sided UC, and backwash ileitis in patients with severe ulcerative pancolitis. Accurate diagnosis requires knowledge of the classic morphological features of UC, as well as a number of atypical pathological presentations that may cause mis-classification of the disease process, either in resection or biopsy specimens. It emphasizes that, although histopathological examination plays a major role in the diagnosis and management of UC, it should always be interpreted in the context of clinical, endoscopic, and radiological findings. This review summarizes diagnostic problems, challenges and advances in ulcerative colitis (UC).
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