Depending on the size of adenoma, increasing amounts of cell alterations of an advanced stage such as high grade dysplasia / intraepithelial neoplasia (HGIN) up to early cancer are found. In these cases, for histo-pathological and oncological reasons, a resection in a solitary manner (en-bloc resection) is necessary to evaluate the completeness of resection properly. Also, former studies showed that recurrence rate could be decreased considerably by en-bloc resections, since the aim is to perform a complete resection basally and laterally. New endoscopic techniques of en-bloc resections have been introduced since a couple of years, using several endoscopic knifes to cut adenoma down after submucosal injection of liquid and consecutively dissect it from the tissue underneath. This technique is mostly called endoscopic submucosal dissection (ESD), and, with not too large adenoma, can be combined with snare resection, too. The complexity of this method though is much larger than that of snare resection. Therefore, the western success rate is considerably less than in Japan, where it was developed first, and where higher numbers of cases exist in the upper GI tract as well as in the lower GI tract. All in all, the complication rate of en-bloc resection is higher than that of snare resection. Those complications, mostly perforations, are endoscopically controllable in most cases, though.