Histological and molecular diversity and heterogeneity of precancerous lesions associated with inflammatory bowel diseases.

AIMS: Inflammatory bowel disease (IBD)-associated precancerous lesions may be adenomatous or non-adenomatous with various histomorphologies. We aim to validate the newly proposed classification, to explore the neoplastic nature of the non-adenomatous lesions and to elucidate the molecular mechanisms underlying the different histomorphologies. METHODS: 44 background precursor lesions identified in 53 cases of surgically resected IBD-associated colorectal and ileal carcinomas were reviewed for the histomorphological features (classified into adenomatous, mucinous, sessile serrated adenoma (SSA)-like, traditional serrated adenoma-like, differentiated, eosinophilic and serrated not otherwise specified (NOS)) and analysed for a key panel of colonic cancer-related molecular markers. RESULTS: Approximately 60% of the lesions were adenomatous, of which some had mixed serrated, mucinous or eosinophilic changes. The remaining non-adenomatous lesions, including all other types except SSA-like type, mostly showed mixed features and focal adenomatous dysplasia. KRAS mutation and p53 mutant-type expression were found in about half cases across all types, while PIK3CA mutation only in some of adenomatous and eosinophilic lesions and MLH1/PMS2 loss in a subset of adenomatous, mucinous and eosinophilic but not in differentiated and serrated lesions. SAT-B2 or PTEN loss and IMP3 overexpression were seen in a small subset of lesions. No BRAF, NRAS or EGFR gene mutation was detected in any type. Certain molecular-morphological correlations were demonstrated; however, no single or combined molecular alteration(s) was specific to any particular morphological type. CONCLUSIONS: IBD-associated precancerous lesions are heterogeneous both histologically and molecularly. True colitis-associated adenomatous lesions are unlikely conventional adenomas. Non-adenomatous lesions without frank cytologic dysplasia should also be regarded as neoplastic.

Similarities and differences in clinical and pathologic features of inflammatory bowel disease-associated colorectal cancer in China and Canada.

BACKGROUND: Colorectal cancer (CRC) has become one of the major life-threatening complications in patients with inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). This study aimed to explore the clinical-pathologic similarities and differences in the IBD-associated CRC (IBD-CRC) between patients in China and Canada. METHODS: Data of 78 patients with IBD-CRC retrospectively retrieved from two representative medical institutions in Beijing (China) and Calgary (Canada) over the same past 13 years, including 25 (22 UC-associated and three CD-associated) from Beijing group and 53 (32 UC-associated and 21 CD-associated) from Calgary group, were compared with regards to their clinical and pathologic characteristics. RESULTS: Several known features of IBD-CRC were seen in both groups, including long duration and large extent of colitis, active inflammation background, multifocal lesions, and advanced tumor-node-metastasis stage. Beijing group showed a significantly higher percentage of UC (88.0% vs. 60.4%, P = 0.018), younger age at diagnosis of CRC (48.6 ±â€Š12.8 years vs. 61.6 ±â€Š14.7 years, P < 0.001), lower ratio of mucinous adenocarcinoma (7.1% vs. 42.4%, P = 0.001) compared with Calgary group. None of the Beijing group had concurrent primary sclerosing cholangitis, while 5.7% of Calgary group did. Surveillance colonoscopy favored the detection rate of precancerous lesions (41.4% vs.17.0%, P = 0.002). CONCLUSIONS: As compared with patients from the Calgary group, the IBD-CRC patients in Beijing group were younger, less CD-associated and had less mucinous features, otherwise they were similar in many common features.

Role of the lymphatic system in the pathogenesis of Crohn's disease.

PURPOSE OF REVIEW: Intestinal lymph containing interstitial fluid, proteins, immune cells, and digested lipids is actively transported back to the blood stream thanks to rhythmical contractions of the mesenteric lymphatic vessels. During this process, lymph flows through several lymph nodes, allowing antigens to be sampled by the immune system. Abnormalities in lymphatic drainage have been noted in the original descriptions of Crohn's disease, but essentially ignored since. The lymphatic system is re-emerging as a critical player in inflammatory and immune processes and the purpose of this review is to present and discuss new concepts related to the involvement of the lymphatic system in the development of inflammatory bowel diseases (IBDs) and more specifically Crohn's disease. RECENT FINDINGS: Recent studies reporting lymphangitis, lymphangiogenesis, bacterial infiltration and lymph node infection, immune cell trafficking, and fat-wrapping in Crohn's disease suggest altered lymph drainage and lymphatic pumping, implicating the lymphatic system as a likely player in inflammatory disorders and IBDs. SUMMARY: Improved knowledge and appreciation of the roles that the lymphatic system plays in immune cell trafficking, infection, fat transport, distribution and metabolism and, of course, edema resolution is necessary to better understand the pathogenesis of chronic inflammatory conditions such as Crohn's disease and may provide the basis for new therapeutic strategies.