A 0-2C laterally spreading tumor non-granular type LSTNG lesion, 40 mm in size, was located in the ascending colon. After indigocarmine dye spraying, the depressed margin was delineated clearly. Narrowband imaging NBI with magnification revealed a type 3a capillary pattern in this shallow depressed area that indicated intramucosal cancer. Magnification colonoscopy with indigocarmine dye revealed a 3S pit pattern in the depressed area of this lesion corresponding to an intramucosal neoplasia. Crystal violet 0.05% staining clearly revealed a slightly irregular VI non-invasive pattern in this depressed area suggesting an intramucosal cancer, thereby indicating that this LSTNG was a good candidate for ESD treatment. The margin of the lesion was delineated before ESD using 0.4% indigocarmine dye spraying in retroflex view. We inject glycerol first to confirm a good submucosal elevation and then inject muco-up in order to keep good submucosal elevation. After creation of the submucosal fluid cushion, an initial incision was made with the ball-tip B-knife at the oral side of the lesion. In colorectal cases, we usually start marginal cutting from oral side in a retroflex view. After partial marginal resection of lesion's oral side, submucosal dissection was begun immediately using the same ball-tip B-knife in retroflex view in forced coagulation mode 50 watts effect 3 or swift coagulation mode 50 watts effect 3. At the beginning submucosal dissection should be performed just under the mucosal layer to prevent perforation. ST Hood short type makes a counterattraction for the resected specimen and submucosal layer can be visualized clearly at this moment. At this moment submucosal layer can be visualized adequately so the submucosal dissection is conducted at the lower third submucosal layer safely. At this moment the knife is approaching to the muscle layer vertically, so careful dissection is necessary. After the lesion was partially dissected so that the submucosal layer could be visualized sufficiently, a new IT knife was used to complete the dissection of the submucosal layer quickly and safely. This is the final dissection using the same IT knife, safely, in 80 minutes. This is the ulcer bed after an on-block ESD and there is no muscle defect or bleeding. It is unnecessary to coagulate all visible vessels after colonic ESD because of the low incidence of delayed bleeding. Too much coagulation will increase the risk of delayed perforation because of thinner colonic wall. Histology revealed submucosal slight invasion and curative resection was achieved.

40mm tumor

0-2C laterally spreading tumor

non-granular type lesion

ascending colon

endoscopic submucosal dissection (ESD)