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AimsThere are no standardized histologic criteria for diagnosing serrated epithelial change (SEC) in inflammatory bowel disease (IBD), but two commonly used definitions are currently in use. The first definition (DEF1) is a simpler definition but requires endoscopic correlation. It encompasses all endoscopically invisible or non‐targeted serrated lesions without morphologic evidence of dysplasia that do not meet the diagnostic criteria of sessile serrated lesion (SSL) or traditional serrated adenoma (TSA). In contrast, the second definition (DEF2) incorporates more complex morphologic criteria (i.e., disorganized crypt architecture with some crypts no longer perpendicular or extending down to the muscularis mucosae, irregular serration spanning the entire thickness of the mucosa, and goblet cell‐rich epithelium), but does not necessitate endoscopic correlation. The reproducibility of SEC diagnoses using these definitions among gastrointestinal (GI) pathologists has not yet been evaluated.Methods and resultsSeven GI pathologists independently evaluated 38 GI cases, including 21 digitally scanned biopsy slides and 17 previously published images, demonstrating various types of serrated changes and their morphologic mimics. The diagnostic categories included: (1) SEC, (2) hyperplastic polyp (HP), (3) SSL, (4) TSA, (5) hypermucinous dysplasia (HMD), and (6) no serrated change or dysplasia (NSD). All cases were selected by a single pathologist (WTC) who did not participate in the interobserver study. The pathologists initially assessed each case as if it were endoscopically normal and provided a diagnosis using DEF1. Next, they re‐evaluated each case, this time considering it as a nodular or polypoid lesion, and again made a diagnosis using DEF1. The same process was then repeated for each case but using DEF2. A total of 532 diagnoses were made for each definition (7 pathologists × 38 cases × 2 endoscopic appearances). Fleiss' kappa statistics were used to assess the level of agreement among the seven pathologists. The total number of SEC diagnoses using DEF1 (n = 110 of 532) was more than twice that of DEF2 (n = 50 of 532). Also, the number of SEC diagnoses per pathologist was higher using DEF1 (mean: 16, range: 12–18) compared to DEF2 (mean: 7, range: 0–14). Furthermore, the instances where four or more pathologists agreed on the diagnosis of SEC were more frequent with DEF1 (16 of 38 cases) than with DEF2 (1 of 38 cases). The overall agreement in diagnosing SEC (vs. no SEC) using DEF1 was substantial (k = 0.69, P < 0.001), whereas the agreement using DEF2 was only slight (k = 0.18, P < 0.001). Among potential SEC mimics, there was substantial agreement in diagnosing HP (k = 0.69 using DEF1), SSL (k = 0.68), TSA (k = 1.00), HMD (k = 0.79), and NSD (k = 0.61) (P < 0.001).ConclusionsThe diagnosis of SEC using DEF1 is significantly more reproducible than using DEF2. Utilizing DEF1 is also less likely to miss potentially important cases of SEC. Therefore, DEF1 could be adopted to separate SEC from other serrated lesions and morphologic mimics in IBD.

AimsThere is a lack of published literature on the diagnostic reproducibility of oesophageal squamous dysplasia using a two‐tiered grading system.Methods and resultsWe identified 75 oesophageal biopsies, which were reviewed by 10 international pathologists twice (1500 total observations) with a > 4‐week washout period. Between rounds, a consensus meeting refining diagnostic criteria was held and an atlas was created to provide illustrations. Overall agreement was fair with kappa of 0.35 and 0.32 in round 1 and 2, respectively. Agreement was moderate to fair for negative for dysplasia (ND) (round 1 = 0.41 and round 2 = 0.34) and poor for indefinite for dysplasia (IND) and low‐grade dysplasia (LGD) (kappa <0.2). Agreement for high‐grade dysplasia (HGD) was good in both rounds (round 1 = 0.64; round 2 = 0.61). In round 1, majority diagnosis (MDx, ≥6 of 10 raters agreeing) was seen in 51 (68%) cases with the majority classified as ND (N = 27) or HGD (N = 18). MDx was rarely achieved for LGD (N = 6). In round 2, MDx was seen in 49 (65%) cases (20 ND, 1 IND, 11 LGD and 17 HGD). Of the 40 cases with MDx for both rounds, 39 were concordant (15 HGD, 6 LGD and 18 ND).ConclusionsOverall agreement among pathologists in diagnosing squamous lesions is fair; however, HGD had good agreement. This study fills an important gap in our knowledge of the inter‐rater variability in the diagnosis of oesophageal squamous dysplasia.

Abstract Context Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was introduced as a new entity replacing the diagnosis of noninvasive encapsulated follicular variant of papillary thyroid carcinoma (PTC). Significant variability in the incidence of NIFTP diagnosed in different world regions has been reported. Objective To investigate the rate of adoption of NIFTP, change in practice patterns, and uniformity in applying diagnostic criteria among pathologists practicing in different regions. Methods Two surveys distributed to pathologists of the International Endocrine Pathology Discussion Group with multiple-choice questions on NIFTP adoption into pathology practice and whole slide images of 5 tumors to collect information on nuclear score and diagnosis. Forty-eight endocrine pathologists, including 24 from North America, 8 from Europe, and 16 from Asia/Oceania completed the first survey and 38 the second survey. Results A 94% adoption rate of NIFTP by the pathologists was found. Yet, the frequency of rendering NIFTP diagnosis was significantly higher in North America than in other regions (P = .009). While the highest concordance was found in diagnosing lesions with mildly or well-developed PTC-like nuclei, there was significant variability in nuclear scoring and diagnosing NIFTP for tumors with moderate nuclear changes (nuclear score 2) (case 2, P &lt; .05). Pathologists practicing in North America and Europe showed a tendency for lower thresholds for PTC-like nuclei and NIFTP than those practicing in Asia/Oceania. Conclusion Despite a high adoption rate of NIFTP across geographic regions, NIFTP is diagnosed more often by pathologists in North America. Significant differences remain in diagnosing intermediate PTC-like nuclei and respectively NIFTP, with more conservative nuclear scoring in Asia/Oceania, which may explain the geographic differences in NIFTP incidence.

SummaryBackgroundColitis is a significant complication of immune checkpoint inhibitors (ICI). Currently, clinical and endoscopic severity are used to guide therapy.AimsTo investigate associations between clinical, endoscopic, and histological features with outcomesMethodsWe identified 149 patients from seven institutions with biopsy‐proven ICI colitis. Biopsies were evaluated for histological features including the Geboes score, and the Robarts histopathological index (RHI) was calculated. Clinical, endoscopic, and histological data were tested for associations with biological use and adverse colitis outcomes (biological‐refractory colitis, colectomy or death from colitis).ResultsThree mutually exclusive histological patterns were identified: acute colitis, chronic active colitis and microscopic colitis. Microscopic colitis was associated with older age (68.5 vs 61 years for acute colitis pattern, P = 0.02) and longer time to colitis (5.5 vs 3 months for the other patterns, P = 0.05). Biological use was associated with earlier time to colitis (2 vs 3 months, P = 0.04) and higher RHI (18 vs 12, P = 0.007). On multivariate analysis, RHI ≥14 was associated with biological use with an odds ratio of 4.5 (95% CI 1.4‐13.8; P = 0.01). Adverse colitis outcomes were associated with shorter time to colitis (2 vs 3 months, P = 0.008) and higher RHI (24 vs 14, P = 0.001). On multivariate analysis, RHI ≥24 was associated with adverse colitis outcomes with an odds ratio 9.5 (95% CI 2.1‐42.3 P = 0.003).ConclusionHistological activity as measured by RHI is the only factor independently associated with biological use and adverse colitis outcomes. Prospective studies are needed to validate these findings to determine if histological activity should be incorporated into therapeutic algorithms.

LINKED CONTENTThis article is linked to Pai et al and Buckle & Christensen papers. To view these articles, visit https://doi.org/10.1111/apt.16142 and https://doi.org/10.1111/apt.16203

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.