Non-conventional mucosal lesions (serrated epithelial change, villous hypermucinous change) are frequent in patients with inflammatory bowel disease-results of molecular and immunohistochemical single institutional study.

Chronically inflamed mucosa in inflammatory bowel disease (IBD) is associated with an increased risk of cancer. Besides IBD-associated dysplasia, there are non-conventional mucosal changes that may act as potential precursors. The aim of the study was to retrospectively review samples from IBD patients focusing on detection of such lesions with evaluation of their immunohistochemical and molecular properties. Surgical specimens and/or endoscopical biopsy samples of IBD patients examined during a 10-year period were reviewed. Detected mucosal lesions were divided into three groups-group 1 (non-conventional or putative precursor lesions - PPLs) with serrated or villous hypermucinous morphology, group 2 (true serrated polyps fulfilling valid criteria), and group 3 (IBD-associated neoplasia). Lesions from all groups were analyzed with antibodies against MLH1, p53, and MGMT and by molecular testing of KRAS, NRAS, and BRAF mutation. Samples from 309 IBD patients were reviewed. A total of 88 mucosal lesions were found in 51 patients. Most common were lesions from group 1 with superficial serrated epithelial change seen in 41 samples (46.6%) and villous hypermucinous change in 6 (6.8%). Group 2 consisted of 15 true serrated polyps. Six conventional IBD-dysplasia cases and 11 carcinomas were seen in group 3. Six lesions from group 1 were associated with invasive carcinoma whereas two shared the same mutation in KRAS or BRAF. Lesions from group 1 were characterized by loss of MGMT expression in 44.6%, aberrant p53 expression, and by mutations in KRAS gene in 42.9% of cases. This study proves the existence of mucosal changes other than conventional IBD-dysplasia and extends the knowledge about their immunohistochemical and molecular properties and relation to carcinoma further supporting their potential role in IBD-related carcinogenesis.