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Background and aims: Pathological studies indicate papillary adenocarcinomas are more aggressive than tubular adenocarcinomas, but a definitive diagnosis is difficult using conventional endoscopy alone. The vessels within an epithelial circle (VEC) pattern, visualized using magnifying endoscopy with narrow-band imaging (ME-NBI), may be a feature of papillary adenocarcinoma. The aims of our study were to investigate whether the VEC pattern is useful in the preoperative diagnosis of papillary adenocarcinoma and to determine whether VEC-positive adenocarcinomas are more malignant than VEC-negative lesions. Patients and materials: From 395 consecutive early gastric cancers resected using the endoscopic submucosal dissection method, we analyzed 35 VEC-positive lesions and 70 VEC-negative control lesions matched for size and macroscopic type. We evaluated (1) the correlation between the incidence of VEC-positive cancers and the histological papillary structure and (2) differences in the incidence of coexisting undifferentiated carcinoma in VEC-positive and VEC-negative cancers and the incidence of submucosal and vascular invasion. Results: Histological papillary structure was seen in 94 % (33/35) of VEC-positive and 9 % (6/70) of VEC-negative cancers, a significant difference ( P < 0.001). The incidence of coexisting undifferentiated carcinoma was 23 % (8/35) in VEC-positive and 3 % (2/70) in VEC-negative cancers ( P = 0.002). The incidence of submucosal invasion by the carcinoma was 26 % (9/35) in VEC-positive cancers and 10 % (7/70) in VEC-negative cancers ( P = 0.045). Conclusions: The VEC pattern as visualized using ME-NBI is a promising preoperative diagnostic marker of papillary adenocarcinoma. Coexisting undifferentiated carcinoma and submucosal invasion were each seen in approximately one fourth of VEC-positive cancers. [ABSTRACT FROM AUTHOR]