Knife-assisted resection (KAR) for small rectal neuroendocrine neoplasia.

Rectal neuroendocrine neoplasia (rNEN) are usually small (<10 mm), well-differentiated (G1/2) lesions arising from the interface between mucosal and submucosal layers; therefore, polypectomy and standard endoscopic mucosal resection (EMR) techniques are usually not curative due to the presence of neoplastic cells on the resection margin, leading to possible tumor recurrence [1].

Ligation-assisted EMR and endoscopic submucosal dissection (ESD) have been proposed as treatment of choice in case of lesions <10 mm without muscolaris propria involvement [1-3]. However, in real practice, most of these lesions undergo standard EMR and are then refereed to tertiary centers in case of incomplete resections [2, 3]. Pagano et al. [4] recently demonstrated that, in those cases, ESD was indicated for lesions >3 mm because of the risk of residual neoplasia.

We report two cases of small (<5 mm) rNEN treated at the time of index colonoscopy with knife-assisted resection (KAR). KAR was initially described and proposed for en bloc resection of colorectal lesions, with incomplete elevation after submucosal injection, due to significant fibrosis [5]. The procedure started with a submucosal injection of methylene blue; then, a circumferential incision with the tip of a standard polypectomy snare (10-mm polypectomy snare, MedItalia, Palermo, Italy) was performed (Endocut Q, effect 3, VIO300D, ERBE, USA); finally, the polypectomy snare was then placed into the submucosal groove to complete the resection (Figure 1 and Supplementary Video 1). En bloc resection was achieved in both cases in <5 minutes with no adverse events. The procedures were completed with the same equipment used in a standard EMR, with no need for dedicated devices. Pathological specimens showed the presence of well-differentiated G1 rNEN with negative lateral and deep resection margins (R0).

Figure 1.

Knife-assisted resection (KAR) for a small neuroendocrine tumor located in lower rectum. (A) A yellowish <10-mm sub-epithelial lesion was found in lower rectum. (B) After placement of a transparent distal attachment, submucosal injection with methylene blue solution was performed in order to create a fluid cushion between the mucosa and the muscolaris propria. (C) The tip of the snare was used to make the first incision in EndoCut Q mode. (D) Circumferential incision with the tip of the snare was performed. (E) After a circumferential incision was completed, the tip of the snare was used to create a 1- to 2-mm submucosal groove. (F) After snare resection, a clear mucosal defect was observed.

In our opinion, KAR might be considered the best treatment strategy for achieving an R0 resection of small rNEN at the time of index colonoscopy; compared to other advanced resection techniques (ESD or ligation-assisted EMR), KAR seems quicker (<5 minutes) and cheaper, without any increased risk of complications. Large comparative studies are needed to confirm this hypothesis.

Supplementary data

Supplementary data is available at Gastroenterology Report online.

Authors’ contributions

A.L. performed the procedures; A.L., S.S. and N.B. drafted the manuscript. A.C. and P.F. prepared the figures and video, and edited the manuscript. All authors reviewed and approved the final version.

Conflicts of interest

None declared.

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