Various subtypes of nonconventional dysplasia have been recently described in inflammatory bowel disease (IBD). We hypothesized that goblet cell deficient dysplasia and serrated dysplasia may be the primary precursor lesions for goblet cell deficient (GCDAC) and serrated (SAC) variants of colonic adenocarcinoma, respectively. Clinicopathologic features of 23 GCDAC and 10 SAC colectomy cases were analyzed. All dysplastic lesions found adjacent to the colorectal cancers (n = 22 for GCDACs and n = 10 for SACs) were subtyped as conventional, nonconventional, or mixed-type dysplasia. As controls, 12 IBD colectomy cases with well to moderately differentiated adenocarcinoma that lacked any mucinous, signet ring cell, low-grade tubuloglandular, or serrated features while retaining goblet cells throughout the tumor (at least 50% of the tumor) were evaluated. The cohort consisted of 19 (58%) men and 14 (42%) women, with a mean age of 53 years and a long history of IBD (mean duration: 18 y). Twenty-seven (82%) patients had ulcerative colitis. GCDACs (57%) were more often flat or invisible than SACs (10%) and controls (25%; P = 0.023). The GCDAC and SAC groups were more likely to show lymphovascular invasion (GCDAC group: 52%, SAC group: 50%, control group: 0%, P = 0.001) and lymph node metastasis (GCDAC group: 39%, SAC group: 50%, control group: 0%, P = 0.009) than the control group. Notably, GCDACs and SACs were more frequently associated with nonconventional dysplasia than controls (GCDAC group: 77%, SAC group: 40%, control group: 0%, P < 0.001). Goblet cell deficient dysplasia (73%) was the most prevalent dysplastic subtype associated with GCDACs ( P = 0.049), whereas dysplasias featuring a serrated component (60%) were most often associated with SACs ( P = 0.001). The GCDAC group (75%) had a higher rate of macroscopically flat or invisible synchronous dysplasia compared with the SAC (20%) and control (33%) groups ( P = 0.045). Synchronous dysplasia demonstrated nonconventional dysplastic features more frequently in the GCDAC (69%) and SAC (40%) groups compared with the control group (0%; P = 0.016). In conclusion, goblet cell deficient dysplasia and dysplasias featuring a serrated component could potentially serve as high-risk markers for GCDACs and SACs, respectively.

The term nonconventional dysplasia has been coined to describe several underrecognized morphologic patterns of epithelial dysplasia in inflammatory bowel disease (IBD), but to date, the full recognition of these newly characterized lesions by pathologists is uneven. The identification of nonconventional dysplastic subtypes is becoming increasingly important, as they often present as invisible/flat dysplasia and are more frequently associated with advanced neoplasia than conventional dysplasia on follow-up. This review describes the morphologic, clinicopathologic, and molecular characteristics of seven nonconventional subtypes known to date, as well as their potential significance in the clinical management of IBD patients.

Compared to the general population, patients with inflammatory bowel disease (IBD), both ulcerative colitis (UC) or Crohn's disease (CD), are at increased risk of developing some cancers, particularly colorectal cancers (CRC). CRCs, the vast majority of which are adenocarcinomas, develop from a precancerous lesion called dysplasia (or intraepithelial neoplasia) via an inflammation-dysplasia-adenocarcinoma sequence. The advancements of new endoscopic techniques, including visualisation and resection techniques, has led to a reclassification of dysplasia lesions into visible and invisible lesions and their therapeutic management, with a more conservative approach to the colorectal setting. In addition, besides conventional dysplasia, of intestinal phenotype, classically described in IBD, non-conventional dysplasias (as opposed to conventional dysplasia of intestinal phenotype) are now described, including at least seven subtypes. Recognition of these unconventional subtypes, which are still poorly known from pathologists, is becoming crucial, as some of these subtypes appear to be at high risk of developing advanced neoplasia (i.e. high-grade dysplasia or CRC). This review briefly describes the macroscopic features of dysplastic lesions in IBD, as well as their therapeutic management, followed by the clinicopathological features of these dysplastic lesions, with particular emphasis on the new subtypes of unconventional dysplasia, both from a morphological and molecular point of view.

Published in 2015, the International Consensus Recommendations on Surveillance for Colorectal Endoscopic Neoplasia Detection and Management in Inflammatory Bowel Disease Patients (SCENIC) recommended abandoning the use of diagnostic term "dysplasia-associated lesion or mass (DALM)" for polypoid dysplastic lesions detected in patients with inflammatory bowel disease (IBD). The aim of this study was to investigate whether this recommendation had any influence on diagnostic terminologies used by pathologists in their practice.

We retrospectively reviewed all pathology reports for surveillance colonoscopic biopsies from ulcerative colitis (UC) patients in our institution during 1/2012-12/2014 (pre-SCENIC) and 1/2016-12/2018 (post-SCENIC). These included 1203 biopsies from 901 UC patients during the pre-SCENIC period and 1273 biopsies from 977 UC patients during the post-SCENIC period. Their corresponding endoscopic findings and histopathologic diagnoses were recorded. Clinical indications for total colectomy for UC patients and corresponding histopathologic findings in colectomy specimens were also recorded and compared.

A total of 347 and 419 polyps/polypoid lesions were identified during the pre-SCENIC and post-SCENIC periods, among which 60 and 104 were dysplastic/adenomatous, respectively. More polypoid dysplastic lesions were simply diagnosed as "adenoma" during the post-SCENIC period in comparison with the pre-SCENIC period (97.1% vs 65.0%; P < 0.001). The number of cases with a comment in pathology reports regarding the distinction between DALM and sporadic adenoma was also significantly decreased during the post-SCENIC period (5.8% vs 38.3%; P < 0.001). In addition, the term "dysplasia" was more consistently used for random biopsies during the post-SCENIC period. Furthermore, the terms "sessile serrated adenoma/polyp" (SSA/P) and "serrated epithelial change" (SEC) were more consistently used for polypoid lesions and random biopsies, respectively, during the post-SCENIC period, although these were not specifically addressed in the SCENIC recommendations. The indications for colectomy remained unchanged, however, despite the standardization of diagnostic terminologies.

The SCENIC recommendations relieve pathologists from the burden of distinguishing DALM from sporadic adenoma in IBD patients, which helps the standardization of diagnostic terminologies used by pathologists. The consistent use of the diagnostic terminologies may help reduce potential confusions to clinicians and patients.

Patients with inflammatory bowel disease are at significantly increased risk of dysplasia and colorectal cancer (CRC). The early detection, histologic grading, and removal of dysplasia plays a critical role in preventing the development of CRC. With advances in endoscopic visualization and resection techniques, colectomy is no longer recommended to manage dysplasia, unless surveillance colonoscopy detects flat/invisible dysplasia (either high-grade dysplasia or multifocal low-grade dysplasia) or an endoscopically unresectable lesion. Although there are numerous review articles and book chapters on the morphologic criteria of conventional (intestinal type) dysplasia, the most well-recognized form of dysplasia, at least 7 distinct nonconventional morphologic patterns of epithelial dysplasia have been recently described in inflammatory bowel disease. Most practicing pathologists are not familiar with these nonconventional subtypes and thus, may even overlook some of these dysplastic lesions as benign or reactive. However, the recognition of these subtypes is important, as some of them appear to have a high risk of developing advanced neoplasia (high-grade dysplasia or CRC) and often show molecular alterations characteristic of advanced neoplasia. This review briefly describes the morphologic criteria of conventional dysplasia but predominantly focuses on all 7 nonconventional subtypes as well as our understanding of their clinicopathologic and molecular features that can assist in their risk stratification.

The increasing use of gastrointestinal endoscopic procedures has led to the recognition by histopathologists of non-conventional (or special-type) dysplasias of the gastrointestinal tract. These lesions can be recognised in association with prevalent underlying gastrointestinal conditions, such as Barrett oesophagus, chronic atrophic gastritis, and inflammatory bowel disease. The diagnosis of these special types can be challenging, and their biological behaviours are not fully characterised. The aim of this review is to provide a global view of non-conventional dysplastic lesions observed in the various segments of the tubular gastrointestinal tract and describe their salient features. Furthermore, as the clinical implications of these various subtypes have not been broadly tested in practice and are not represented in most management guidelines, we offer guidance on the best management practices for these lesions.