Clinical outcomes of endoscopic submucosal dissection for undifferentiated early gastric cancer

Early gastric cancer (EGC) with undifferentiated histology has not been generally accepted as an indication for endoscopic treatment. This study was designed to evaluate the outcomes and clinicopathological factors associated with the complete resection of undifferentiated EGC using endoscopic submucosal dissection (ESD). A retrospective analysis of prospectively collected data was performed on consecutive patients who underwent ESD. Among the 456 EGCs treated using ESD at the Seoul National University Hospital, Seoul, Korea, between April 2005 and June 2008, 60 lesions (13.2%) were diagnosed as undifferentiated gastric cancer (poorly differentiated adenocarcinoma or signet ring cell carcinoma). En bloc resection was performed in all lesions without significant complications. The size discrepancy between the pretreatment endoscopy and the resected specimen was significantly higher in undifferentiated EGCs than differentiated EGCs (p = 0.002). The complete resection rate was significantly lower for undifferentiated EGC (55%) cases than differentiated EGC cases (84.1%; p < 0.001). Independent risk factors for incomplete resection of undifferentiated EGC included tumor size > 20 mm, submucosal invasion, and presence of ulceration. During a mean observation time of 16 months, no recurrence developed in any of the patients with undifferentiated EGCs thought to be completely resected by ESD. ESD might be considered an alternative treatment modality in carefully selected cases of undifferentiated EGC.