Incomplete mucosal layer excision during EMR: a potential source of recurrent adenoma (with video).

BACKGROUND AND AIMS: Residual or recurrent adenoma (RRA) detected during surveillance is the major limitation of EMR. The pathogenesis of RRA is unknown, although thermal ablation of the post-endoscopic resection defect (PED) margin reduces RRA. We aimed to identify a feature within the PED that could be associated with RRA.

METHODS

Between January 2017 and July 2020, detailed prospective procedural data on all EMR procedures performed at a single center were retrospectively analyzed. At the completion of EMR, the PED was systematically examined for features of incomplete mucosal layer excision (IME). This was defined as a demarcated area within the PED bordered by a white electrocautery ring and containing endoscopically identifiable features suggesting incomplete resection of the mucosa including lacy capillaries and/or visible fibers of the muscularis mucosae. Areas of IME were reinjected and re-excised by snare and submitted separately for blinded specialist GI pathologist review.

RESULTS

EMR was performed for 508 large nonpedunculated colorectal polyps (LNPCPs) (median size, 35 mm). In 10 PEDs (2.0%), an area of IME was identified and excised. Histopathologic examination of areas of suspected IME demonstrated muscularis mucosae in 9 of 10 (90%), residual lamina propria in 9 of 10 (90.0%), and residual adenoma in 5 of 10 (50.0%). No RRA was detected during follow-up after re-excision of IME.

CONCLUSIONS

We report the novel finding of IME within the PED after EMR of LNPCPs. IME may contain microscopic residual adenoma and therefore is a risk for RRA during follow-up. After completion of EMR, the PED should be carefully evaluated. If IME is found, it should be excised. (Clinical trial registration number: NCT01368289 and NCT02000141.).