Second lesions located within the same belt-like region along the stomach's short axis as primary lesions: Boundary equal lesion trends

Background and study aims: Gastric adenoma and cancer are common in Asia, with early detection critical for prognosis. Synchronous multiple early gastric cancers (SMEGCs) occur in 6% to 14% of cases, but their clinicopathological characteristics remain unclear. This study analyzed synchronous multiple gastric neoplasms treated by endoscopic resection or surgery to aid early detection. Patients and methods: Among 2,991 cases of early gastric cancer or adenoma diagnosed at our institution, 173 patients with 346 synchronous lesions (January 2016-March 2024) were analyzed. All lesions were mucosal or submucosal. Lesions were categorized as "1st" (larger) and "2nd" (smaller), and clinicopathological characteristics were compared using Chi-square and Fisher's exact tests with Cramér's V. Results: Patients had a mean age of 73.2 years; 72.8% were male. Most lesions were in the lower/middle stomach, differentiated (92.2%), depressed (52.9%), and brownish on narrow-band imaging (65.3%). Mean tumor diameter was 13.4 mm. Although 1st lesions were larger, other features showed high concordance (≥ 0.25 Cramér's V) in location, morphology, histology, invasion depth, and coloration. Survival was 94.8% (nine unrelated deaths). Conclusions: Synchronous multiple gastric neoplasms tend to have similar endoscopic and histopathologic features and often occur within the same belt-like region along the short axis of the stomach. This pattern was named boundary equal lesions trends (BELT). When detecting one lesion, considering BELT is essential.