Chronic idiopathic inflammatory bowel disease (IBD) with extensive colonic involvement predisposes to the development of colorectal adenocarcinoma. Among the types of cancer occurring in this setting is an unusually well-differentiated low-grade tubuloglandular adenocarcinoma (LGTGA) that has not been studied systematically thus far. A review of 149 IBD-associated cancer resections performed at our institution yielded 17 patients (11%) with 21 tumors classified as LGTGA based on the following histologic characteristics: very well-differentiated small to medium diameter glands with round or tubular profiles, low-grade cytologic characteristics and absence or paucity of desmoplastic reaction. Twelve patients had ulcerative colitis, 4 Crohn disease, and 1 indeterminate colitis. Their median age was 41.5 years (range, 28 to 58 y). Five patients had separate synchronous cancers of conventional types. LGTGAs ranged from 0.4 to 10 cm in size and varied in gross appearance. They included 5 flat lesions that were not identified visually but were detected either by palpation of the unfixed surgical specimen (1 case) or histologically in random sections (4 cases). The invasive glands usually bore a close histologic resemblance to overlying low-grade or indefinite dysplastic crypts. Twelve carcinomas (57%) with well-defined superficial regions of LGTGA progressed histologically to conventional adenocarcinoma in deeper regions. These tumors were significantly more advanced than 9 carcinomas that maintained low-grade histology throughout. Follow-up of 13 patients (76%) for a mean 4.0 years (range, 0.75 to 9.0 y) disclosed 10 (77%) with favorable outcomes and 3 (23%) with adverse outcomes. Two adverse outcomes were attributable to synchronous advanced-stage conventional cancers and the third to progression from LGTGA to poorly differentiated adenocarcinoma. The mucosa overlying and surrounding LGTGA showed low-grade dysplasia (LGD) in 18 cases (86%), indefinite dysplasia with focal LGD in 1 case (5%), and LGD with focal high-grade dysplasia (HGD) in 2 cases (10%). Immunohistochemical studies disclosed expression of MUC2 in 72%, MUC6 in 0%, CK7 in 69%, and CK20 in 100%. Coexpression of CK7 and CK20 was conserved in regions of conventional adenocarcinoma derived from LGTGA. Silencing of immunohistochemical expression of hMLH1 occurred in 6 of 11 tumors tested (55%), implicating defective DNA replication error repair in their pathogenesis. We conclude that LGTGA is a distinct clinicopathologic entity characterized by direct derivation from LGD mucosa of IBD, very well-differentiated morphology, frequent coexpression of CK7 and CK20, and frequent silencing of hMLH1. Histologic progression from LGTGA to conventional types of adenocarcinoma parallels clinical progression to more aggressive neoplasia. The potential of LGD to give rise directly to LGTGA, and by way of LGTGA to more aggressive cancers, reinforces recommendations in favor of aggressive management of IBD patients diagnosed with LGD.
"In addition, UC-associated CRCs are more often well-differentiated (about 34%) . Low-grade tubuloglandular adenocarcinomas, extremely well-differentiated adenocarcinomas rarely encountered outside the setting of colitis, account for 11% of IBD-associated CRC (Figure 10) . "
[Show abstract][Hide abstract] ABSTRACT: This review summarizes diagnostic problems, challenges and advances in ulcerative colitis (UC). 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. 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. 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. 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. Indeterminate colitis should only be used in colectomy specimens as a provisional pathological diagnosis. 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. Colon biopsy from UC patients should always be evaluated for dysplasia based on cytological and architectural abnormalities. Accurate interpretation and classification of dysplasia in colon biopsy from UC patients as sporadic adenoma or UC-related dysplasia [flat, adenoma-like, or dysplasia-associated lesion or mass (DALM)] requires clinical and endoscopic correlation. 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. Recent data suggest that such lesions may be treated adequately by polypectomy in the absence of flat dysplasia in the patient. UC patients with DALM or flat high-grade dysplasia should be treated by colectomy because of the high probability of adenocarcinoma. 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. The surveillance interval and treatment options for UC patients with dysplasia are reviewed in detail.
[Show abstract][Hide abstract] ABSTRACT: Gastrointestinal histopathology represents approximately half of the current work-flow in our laboratory, and six to ten of
the reports signed out daily concern patients studied for Crohn’s disease (CD). This chapter summarizes the role of the pathologist
in the management of patients with CD, starting from a glossary of the terms used in the information exchange between the
pathologist radiologist gastroenterologist, and surgeon. This multidisciplinary team approach is crucial for the correct management
of CD patients. The gastrointestinal tract has limited patterns of tissue response to triggers of inflammation and the diagnosis
therefore relies upon the various combinations of these patterns with the clinical picture. The study of endoscopic specimens
is based not only on a histopathological scheme but also on the presentation of the patient, which is of equal importance.
Due to the limits in the information that can be extracted by studying the morphology of inflammation, molecular biology is
expected to play an increasingly important role in providing the clinician with insight into the disease process in a single
CD patient and thus in allowing the appropriate treatment strategy to be tailored accordingly.
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