For the ESD procedure, a single-channel upper gastrointestinal endoscope with a water-jet system (GIF-Q260J, Olympus Medical Systems, Tokyo, Japan) was used with a transparent cap attached to the endoscope tip. Circumferential markings were made on the proximal and distal sides of the normal-appearing mucosa at least 5 mm from the lesions. A high-frequency generator (VIO300D; ERBE Elektromedizin GmbH, Tübingen, Germany) was set at the forced coagulation mode (Effect 2, output 40 W) to incise the mucosa. A ready-to-use hyaluronic acid solution (MucoUp, Seikagaku Co., Tokyo, Japan) was injected into the submucosal layer to lift the surrounding mucosa. The distal mucosal incision was completed first all the way around the markings with the FlushKnife (Fujinon-Toshiba ES System Co, Omiya, Japan) under the Endo cut I mode (Effect 4, Duration 2, Interval 3). The proximal mucosa was then incised in the same circular fashion. The submucosa was incised using the FlushKnife under the forced coagulation mode (Effect 2, output 40 W), starting beneath the proximal mucosal incision in each quadrant. The submucosal dissection was advanced to reach the distal side of the mucosal incision, thus creating a submucosal tunnel. Then, the submucosa between the 4 longitudinal tunnels was dissected to connect together until the lesion was detached. To control bleeding during ESD or to prevent possible bleeding from visible vessels in the artificial ulcer immediately after resection, a hemostatic forceps (Coagrasper, Olympus) was used in the soft coagulation mode (Effect 5, 60 W). Each patient was sedated by intravenous injection of 7.5 mg diazepam and 50 mg pethidine, and additional diazepam (2.5 mg) or pethidine (25 mg) was given alternately as needed for conscious sedation throughout ESD. CO
2 insufflation was used during the procedure. Procedure-related bleeding after ESD was defined as bleeding that required transfusion or surgical intervention or bleeding that caused the hemoglobin level to fall by 2 g/dL [
13]. Procedure-related perforation was diagnosed endoscopically or by the presence of free air on a plain chest X-ray and chest computed tomogram (CT) [
5]. Longitudinal diameter was measured from the oral edge to the anal edge of resected specimens that were stretched appropriately. The tumor longitudinal diameter was also documented. Excised specimens were fixed in 10% buffered formalin, paraffin-embedded, sectioned perpendicularly at 2-mm intervals, and stained with hematoxylin and eosin.
En bloc resection refers to resection in one-piece [
14]. Follow-up endoscopy with iodine staining and contrast-enhanced CT of the cervix, thorax, and abdomen were scheduled at 3, 6, and 12 months after ESD and then annually thereafter. Biopsy specimens during each follow-up endoscopy were taken from any mucosal abnormalities to assess the presence of local recurrent tumor.