Long-term outcomes of early gastric cancer diagnosed as mixed adenocarcinoma after endoscopic submucosal dissection

Background and Aims: The clinical significance and prognosis of mixed adenocarcinoma in early gastric cancer (EGC) are incompletely understood. The aim of this study was to evaluate the clinicopathological characteristics and long-term outcomes of mixed adenocarcinoma diagnosed as EGC after endoscopic submucosal dissection (ESD). Methods: There were 430 EGCs histologically proven by ESD in 395 patients. The clinicopathological characteristics and long-term outcomes, including the rates of local recurrence, were evaluated according to histological type in EGC treated with ESD. Results: In total, 430 EGCs were classified as 362 (84.4%) tubular adenocarcinomas, 41 (9.5%) poorly cohesive carcinomas (PCCs), 26 (6.0%) mixed adenocarcinomas, and 1 (0.2%) papillary adenocarcinoma according to the World Health Organization classification. Although the en bloc resection rate was acceptable (92.3%) for mixed adenocarcinoma, the complete resection rate was lower (53.8%) than those in other types (P < 0.01). Local recurrence occurred in 5 (19.2%) of 26 mixed adenocarcinomas after ESD. In a multivariate analysis, mixed adenocarcinoma was an independent risk factor predicting local recurrence after ESD for EGC (hazard ratio, 7.039; P < 0.01). Conclusion: Mixed adenocarcinoma is more aggressive than other histological types of EGC based on clinical outcomes. Moreover, it is an independent prognostic factor for local recurrence after ESD for EGC.