This large case series highlights recent advancement in endoscopic management of mucosal lesions of the colon and presents the method with useful figures. We would like to draw attention to a number of details. It would have been useful to have more detail relating to perforation regarding the size, site and type of polyp resected. While one would expect a higher perforation rate on the right side of the colon, in the elderly, or with tumours with deeper invasion level, the authors have not commented on these issues.

Overall, 48 lesions were in the rectum or sigmoid, a region that can be more technically difficult to consider for operative intervention. Presence of lymph nodes for a T1 lesion of colonic wall will change consideration of chemotherapy and corresponds to a 10% difference in survival at 5 years [1]. Endoscopic ultrasound, particularly in this region, can best determine the depth of invasion of polyps, with accuracy of 61–83% for lymph node (N) and 93% for T staging [2]. This can be further supplemented with magnetic resonance imaging (MRI), which in turn has accuracy of 83% for N staging and nearly 100% for T staging [2, 3], although we appreciate that this does not apply for lesions above the peritoneal fold of rectum or the rest of the colon, with some studies quoting only 54% specificity and 75% accuracy [4]. Pre-procedural assessment is important to avoid sub-optimal management, and in this series there were 27 cases of carcinoma that could have been affected. As the case series considered in situ and T1 lesions, longer follow-up for comparison with those managed under currently established criteria of cancer management should be considered.

Considering all these issues with the available current evidence, we feel that, while promising, endoscopic submucosal dissection (ESD) technique may not be ideal for rectal or other distal lesions (within 25 cm of the anal verge) that are amenable to transanal excision or transanal endoscopic micro-surgery (TEMS).