Therapeutic outcomes of endoscopic submucosal dissection of undifferentiated-type intramucosal gastric cancer without ulceration and preoperatively diagnosed as 20 millimetres or less in diameter.

Objective: The aim of the present study was to examine therapeutic outcomes of endoscopic submucosal dissection (ESD) of undifferentiated-type intramucosal gastric cancer and the problems of diagnosis.

Methods: We reviewed 58 patients with preoperatively diagnosed undifferentiated-type intramucosal early gastric cancer (EGC) without ulceration with a diameter of 20 mm or smaller (expanded-indication lesion) who underwent ESD at the Cancer Institute Hospital between September 2003 and August 2008.

Results: The overall rates of one-piece resection and complete resection were 98% and 90% respectively, and the median operation time was 70 min. Bleeding was seen in 8.6% and perforation in 3.4%. The curative resection rate was low at 79%. Factors responsible for non-curative resection were most commonly submucosal invasions. If limited to pathologically diagnosed expanded-indication lesions, the curative resection rate was 98%. The difference in tumor size between a macroscopic diameter and a histological diameter was within +/-5 mm in 96% of expanded-indication lesions, with none of these cases having a histological diameter that exceeded the macroscopic diameter by more than 5 mm.

Conclusions: ESD was technically feasible for expanded-indication lesions of undifferentiated-type EGC. We achieved a high rate of curative resection by the markings at sites 5 mm beyond the preoperatively determined lesion area. Factors responsible for non-curative resection were most commonly submucosal invasions. We should diagnose the depth of such lesions more carefully.