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Background: Barrett's esophagus (BE)-related neoplasia remains less prevalent in Japan than in Western countries; however, its incidence is steadily rising. While multimodal treatment - typically endoscopic resection (ER) followed by ablation - is the standard of care, ER alone remains the primary treatment strategy in Japan. With advances in endoscopic techniques, endoscopic submucosal dissection (ESD) has become the mainstay for managing BE-related neoplasia. This review outlines the current Japanese approach, focusing on indications, preoperative assessment, treatment outcomes, and post-resection surveillance practices within the Japanese clinical context.

Summary: Accurate endoscopic assessment, including the use of magnifying endoscopy with image-enhanced modalities, is central to Japanese practice due to the importance of complete resection of neoplasia in the absence of ablative therapy. While data on BE-related neoplasia remain relatively limited in Japan, several multicenter studies have demonstrated favorable outcomes for ESD in terms of resection quality, safety, and long-term survival, particularly in low-risk patients. However, challenges remain, including the lack of standardized surveillance protocols and considerable heterogeneity in clinical practice across institutions. The establishment of unified clinical pathways and evidence-based strategies will be essential to address the increasing burden of BE-related neoplasia in Japan.

Key messages: The incidence of BE and esophageal adenocarcinoma is increasing in Japan, although still significantly lower than in Western countries. Unlike the Western standard of combining ER with radiofrequency ablation (RFA), Japanese practice relies primarily on ESD as the main curative modality. RFA is not widely available in Japan, leading to a reliance on complete resection and more aggressive ER strategies. Surveillance strategies remain inconsistent, largely due to the lower disease prevalence and limited Japan-specific clinical evidence.

Background: Barrett's esophagus (BE) is the replacement of normal squamous epithelium in the distal esophagus by columnar epithelium. The prognosis of esophageal adenocarcinoma depends largely on the stage at diagnosis. Advances in endoscopic imaging and quality standards have significantly improved the early detection of BE-associated neoplasia. This review summarizes current classification systems, sampling protocols, and adjunct tools for diagnosing early neoplasia in BE in Western practice.

Summary: In Western practice, the diagnosis of BE relies on consensus criteria requiring endoscopic evidence and histopathological confirmation of columnar epithelium proximal to the gastroesophageal junction. However, there are discrepancies regarding the minimum BE extent and the necessity of intestinal metaplasia for diagnosis. Detecting early neoplasia in BE is challenging due to the flat and subtle nature of dysplastic lesions. High-definition white-light endoscopy (HD-WLE) is the standard modality for BE surveillance and is used to assess for characteristic features of neoplasia, including nodularity, surface irregularity, color changes, and demarcated areas. Image-enhancing techniques - such as virtual chromoendoscopy (e.g., narrow-band imaging [NBI], texture and color enhancement imaging [TXI], blue light imaging [BLI], linked color imaging [LCI]), and acetic acid chromoendoscopy - have improved dysplasia detection when applied alongside validated classification systems. Despite technological advances, random four-quadrant biopsies (4QBs) remain the standard for dysplasia detection. Estimating lesion depth is based primarily on HD-WLE, with limited contribution from chromoendoscopy and ancillary imaging techniques (i.e., endoscopic ultrasound [EUS], confocal laser endomicroscopy, optical coherence tomography).

Key messages: Early Barrett's neoplasia is challenging to detect. HD-WLE and image-enhancing techniques improve visualization, but random 4QBs remain central to the diagnostic process. Lesion depth is primarily assessed using endoscopic features and, to a limited extent, ancillary techniques.

Background: Barrett's esophagus (BE) is becoming increasingly prevalent in both Western countries and Japan. Early diagnosis of Barrett's neoplasia remains challenging. Traditionally, the Seattle protocol, a four-quadrant random biopsy method, has been recommended in Western guidelines. However, this approach has several limitations, including sampling errors, poor adherence, and a high procedural burden. Therefore, magnifying endoscopy has gained attention as a valuable tool for detecting and characterizing neoplastic lesions in patients with BE.

Summary: This review outlines historical and current developments in magnifying endoscopic classification systems for BE, with a focus on narrow-band imaging (NBI) and acetic acid chromoendoscopy in both Western countries and Japan. Although various NBI-based classifications have been proposed, their complexity and poor reproducibility have limited their widespread clinical adoption. Recently, simplified and standardized classification systems, including the Barrett's International NBI Group classification in the West and the Japan Esophageal Society-Barrett's esophagus classification in Japan, have been introduced. These systems adopt a binary framework, categorizing mucosal and vascular patterns as "regular" (non-neoplastic) or "irregular" (neoplastic). They are easy to apply and have demonstrated high diagnostic accuracy and substantial interobserver agreement. Further simplification and practical refinement are required for broader clinical implementation.

Key messages: Compared with other gastrointestinal cancers, the magnifying endoscopic diagnosis of Barrett's neoplasia remains technically demanding. However, based on a growing body of evidence, endoscopists should be encouraged to actively challenge this area. Continued efforts to simplify and validate the classification systems are essential for their widespread clinical use in BE surveillance.

Background: Barrett's esophagus (BE) represents the only established precursor to esophageal adenocarcinoma. While endoscopic surveillance is a cornerstone of early detection, it remains limited by interobserver variability, sampling error, and variability in diagnostic yield. In recent years, artificial intelligence (AI) has emerged as a promising tool to improve the detection and characterization of neoplastic lesions in BE.

Summary: This review outlines the current landscape and future potential of AI applications in the endoscopic management of BE. Diagnostic systems employing convolutional neural networks and transformer-based architectures have achieved high performance for both lesion detection (CADe) and characterization (CADx), with several models externally validated in multicenter cohorts. The first CE-certified commercial system, CADU™, has further marked the entry of AI into clinical use. Emerging developments include AI tools for infiltration depth estimation, vessel detection during endoscopic submucosal dissection, post-therapeutic surveillance, and procedural quality assessment. Challenges related to generalizability, human-AI interaction, ethical implementation, and regulatory compliance are discussed in the context of clinical translation.

Key messages: (1) AI systems demonstrate high diagnostic accuracy and enable real-time assistance in BE surveillance. (2) In-domain pretrained models and transformer-based systems may improve robustness and adaptability. (3) Clinical applications are expanding beyond diagnostics to therapeutic guidance and posttreatment monitoring. (4) Successful implementation depends on rigorous validation, explainability, and integration into clinical workflows.

Background: Barrett's esophagus and its malignant progression to Barrett's adenocarcinoma are becoming increasingly prevalent worldwide, yet their underlying mechanisms remain incompletely understood.

Summary: The pathogenesis of Barrett's esophagus and Barrett's adenocarcinoma is multifactorial, involving environmental, genetic, and cellular factors. Chronic acid and bile reflux are well-established contributors, promoting cellular transformation in the esophageal epithelium. Obesity further exacerbates this risk, both indirectly by increasing reflux and directly via proinflammatory adipokines. Recent genetic studies have identified several genetic risk variants, with loss of p53 recognized as critical event in malignant progression. Moreover, the origin of Barrett's esophagus remains under investigation, with proposed sources including cells of esophageal submucosal glands, cells of gastric cardia, and circulating bone marrow-derived cells.

Key messages: The pathophysiological mechanisms underlying Barrett's esophagus and the development of Barrett's adenocarcinoma are still under active investigation. Understanding these mechanisms is essential for developing effective preventive and therapeutic strategies.

Background: With a 50-year delay compared to Europe and the USA, esophageal adenocarcinoma (EAC) began to increase in Japan around 2010, and it is expected to continue rising over the next few decades. This 50-year discrepancy is primarily attributable to variations in the timing of the decline in Helicobacter pylori infection rates across the two regions, with the extent of obesity in Japan also exerting an influence on the projected increase in EAC. Currently, the incidence of EAC in Japan is approximately one-tenth to one-twentieth that observed in Europe and the USA. However, ongoing monitoring is essential to assess the potential for escalation of this cancer. Accurate estimation of the incidence of EAC in Barrett's esophagus (BE), a precancerous condition of EAC, is imperative for the establishment of appropriate endoscopic surveillance for early cancer detection.

Summary: The incidence of EAC in BE is largely determined by its length. In the Japanese population, BE with a length greater than 3 centimeters exhibits a high incidence of EAC and necessitates surveillance, while BE with a length less than 1 centimeter exhibits an exceptionally low incidence of EAC and is considered to require no surveillance. The challenge lies in determining the optimal approach for addressing BE with a length of 1-3 cm, which is observed in 5-15 percent of endoscopic examinees, necessitating careful consideration due to its significance.

Key message: Since the EAC risk of BE varies greatly depending on its length, the need for surveillance and inspection intervals for BE in Japan should be defined by its length.

Background: Barrett's oesophagus (BE) is the sole established precursor to oesophageal adenocarcinoma, with striking contrasts in its epidemiology and management between the East and the West.

Summary: This review, based on a structured literature search, examines the key divergences in endoscopic management: highlighting the Western emphasis on eradication therapy using ablation techniques such as radiofrequency ablation, contrasted with the Eastern expertise in advanced resection techniques including endoscopic submucosal dissection.

Key messages: Despite improving patient outcomes, significant challenges remain, including variable surveillance protocols, controversies regarding non-dysplastic BE and low-grade dysplasia, and optimal strategies for recurrent disease. As gastroesophageal reflux disease and long-segment BE rise in prevalence in the East, and Western proficiency in endoscopic submucosal dissection grows, these once-distinct approaches are poised to converge. As these treatment paradigms align, patients and clinicians alike stand to benefit from more effective, tailored care and better long-term outcomes.

Introduction: Conventional endoscopic mucosal resection (EMR) is widely accepted for 6-20 mm superficial non-ampullary duodenal epithelial tumors (SNADETs); however, its en bloc and R0 resection rates remain suboptimal. Modified techniques, such as underwater EMR (UEMR) and cap-assisted EMR (EMRC), have been introduced to improve outcomes; nevertheless, comparative data are limited despite both techniques being increasingly utilized.

Methods: This retrospective two-center study included patients with 6-20 mm SNADETs treated with either UEMR or EMRC between April 2016 and May 2024 at Kobe University Hospital and the International Clinical Cancer Research Center. Clinicopathologic characteristics, therapeutic outcomes, and adverse events were compared. Multivariate logistic regression analysis was conducted to identify risk factors for non-R0 and piecemeal resection.

Results: A total of 155 SNADETs (51 UEMR, 104 EMRC) were included. The EMRC group achieved significantly higher R0 resection rates (86.5% vs. 62.7%; p < 0.001) and en bloc resection rates (94.2% vs. 78.4%; p = 0.003) without increasing adverse events. Multivariate analysis identified UEMR, lesion size ≥10 mm, and anterior or lateral wall involvement as independent risk factors for non-R0 resection. Lesion size ≥10 mm was the only independent risk factor for piecemeal resection.

Conclusion: In SNADETs measuring 6-20 mm, EMRC demonstrated higher en bloc and R0 resection rates than UEMR with a comparable safety profile, suggesting EMRC may be a useful option for achieving complete resection in selected cases. Prospective studies are needed to refine techniques to minimize complications while maintaining efficacy and to clarify long-term outcomes and recurrence.

Introduction: Achalasia is an esophageal motility disorder that significantly impairs quality of life. Recently, peroral endoscopic myotomy has yielded satisfactory treatment outcomes. Although the current gold standard is esophageal high-resolution manometry (HRM), early endoscopic detection is essential for accurate diagnosis. Dilatation of the esophageal lumen during endoscopy is subjective and has not been fully evaluated. We focused on the extramural compression of the vertebrae in the esophagus, which may reflect dilatation of the esophageal lumen, named the endoscopic vertebrae sign (EVS), and examined the possibility of the EVS as a novel endoscopic finding of achalasia.

Methods: Forty-three patients were diagnosed with achalasia using HRM between July 2013 and November 2022. Five who underwent surgical treatment and one for whom esophagogram was unavailable were excluded, resulting in 37 patients in the achalasia group. Among those who underwent comprehensive medical checkups and esophagogastroduodenoscopy screening at our hospital during the same period, all age- and sex-matched individuals were randomly extracted and 74 were set as controls. The rates of EVS, endoscopic esophageal dilatation at the endoscopist's discretion, and number of visible vertebrae in a single endoscopic view were retrospectively analyzed.

Results: In the achalasia group, the proportion with EVS was 86.5%, with endoscopic esophageal dilatation at the endoscopist's discretion 76%, and the number of visible vertebrae in patients with EVS was 3.2±0.9. These findings differed significantly in controls: 9.5%, 0%, and 1.4±0.4, respectively (p<0.001).

Conclusion: EVS may be one of the endoscopic findings associated with esophageal dilatation and suggestive of achalasia.

Background: Gastric cancer (GC) has a significant impact in Asia. Delay in diagnosis and treatment leads to increased mortality and morbidity. The detection of gastric intestinal metaplasia (GIM) has the potential to be an early sign of GC, but there are controversies. Differences in GC and pre-cancerous lesions between Asians and non-Asians have also contributed to this controversy.

Summary: GIM is a risk factor for developing GC in Asian adults, with more recent meta-analyses demonstrating a 3-4 risk in such patients. Certain GIM subtypes are more likely to develop GC, with Asian patients appearing to have more severe, diffuse, and high-risk subtypes of GIM compared to non-Asians. As a result, most international guidelines recommend endoscopic surveillance in adults with GIM, but this review article suggests it should be targeted towards those with high-risk features. This review also highlights other factors, apart from gastric histology, which are relevant in the development of GC. Factors such as Helicobacter pylori virulence, molecular and genetic mechanisms, gut microbiota, specific dietary components, and social habits as risk factors for GC are discussed.

Key messages: GIM is a risk factor for GC in the Asian population. Surveillance in a targeted population is beneficial.