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Background and aims: At specialized facilities, endoscopic submucosal dissection (ESD) has currently been performed even for difficult cases such as tumors extending to a diverticulum that previously required surgery. This study aims to classify the type of lesion according to the degree of infiltration to a diverticulum and assessed the safety and efficacy of ESD for each type of lesion. Methods: We retrospectively reviewed ESD for lesions at NTT Medical Center Tokyo between January 2014 and April 2019. Lesions were classified as follows: Type 1: lesions in contact with or within 3 mm of the edge of a diverticulum; Type 2: lesions that partially infiltrated into a diverticulum; and Type 3: lesions that infiltrated into and completely covered the diverticulum. Furthermore, ESD strategies were divided into A and B, which indicates that a lesion was resected separately from the diverticulum and along the entire diverticulum, respectively. The clinicopathological characteristics and clinical outcomes were analyzed according to the strategy. Results: A total of 47 lesions satisfied inclusion criteria (19 Type 1, 12 Type 2, and 16 Type 3 lesions). 19 Type 1 and 8 Type 2 lesions were resected using Strategy A, while 4 Type 2 and 16 Type 3 lesions were resected using Strategy B. En bloc resection was achieved in all cases. In Strategy A, the R0 resection rate was 96.3% and the curative resection rate was 88.9%. On the contrary, in Strategy B, the R0 resection rate was 95.0% and the curative resection rate was 90.0%. In Strategy B, one of the patients developed post-operative bleeding that required endoscopic hemostasis; another patient developed delayed perforation that required emergency surgery. Conclusions: ESD for colorectal neoplasms in proximity or extending to a diverticulum is challenging, but this procedure can be a safe and effective therapeutic option.

Since the endoscopic resection of laterally spreading tumors (LSTs) involving the appendiceal orifice remains technically difficult, such lesions are usually treated by surgical resection. However, with recent advances in endoscopic devices, endoscopic submucosal dissection (ESD) has become feasible and may be safely performed even for lesions involving the appendiceal orifice. Therefore, in order to assess the validity of endoscopic treatment for such lesions, we retrospectively evaluated the safety and efficacy of ESD. A total of 30 patients with LSTs extending to within 10 mm of the appendiceal orifice (Group AO) and 122 patients with cecal LSTs located away from the appendiceal orifice (Group C) who were treated between December 2011 and September 2015 were retrospectively enrolled in the present study. The indications for ESD were determined by the preoperative endoscopic diagnosis made on the basis of Kudo’s pit pattern classification. Based on these preoperative endoscopic diagnoses, 8 of the 30 enrolled patients underwent surgical resection as the initial treatment, because the tumor showed deep invasion beyond the orifice and/or a VN pit pattern was visible. The treatment outcomes (en blocR0 resection rates, tumor size, procedure time, and complication rates) were compared between the two groups. The sensitivity and specificity for the cancer diagnosis were 81.8 and 94.7%, respectively. There was no significant difference in the en blocR0 resection rate between Group AO and Group C (90.9 vs. 95.9%, P= 0.23). Furthermore, there were also no differences in the mean tumor size (30.0 ± 20.8 vs. 34.9 ± 14.5 mm, P= 0.17) or mean OR time (55.0 ± 39.2 vs. 58.9 ± 48.2 min P= 0.72) between the two groups. One case from Group AO (4.5%) was complicated by a perforation, which was successfully managed endoscopically. Although proficiency in endoscopic techniques is required, our results indicate that LSTs involving the appendiceal orifice can be successfully treated by ESD.