PTH-063 Suspicion of deep submucosal invasion during endoscopic submucosal dissection: significance of the muscle-retracting sign

Introduction Colorectal endoscopic submucosal dissection (ESD) is a well-established minimally invasive resection technique. When the so-called muscle-retracting (MR) sign is encountered during ESD, complete resection may not be feasible. The pocket creation method (PCM) allows easier recognition of the submucosal space in the context of fibrosis and MR sign. To date, both magnifying endoscopy and endoscopic ultrasound may not be able to show invasive cancer, especially for lateral spreading tumor (LST) with a large nodule. Therefore it may be difficult to predict if any MR sign is caused by fibrosis or deep submucosal invasion. Methods Our aim was to highlight the characteristics of deep submucosal invasion during PCM-ESD. A 74-year-old man had a colonoscopy due to haematochezia and a large granular, mixed-nodular LST was identified in the proximal rectum. Endoscopic assessment of the lesion with near focus, indigo carmine and narrow band imaging (NBI) did not reveal any sign of Kudo pit pattern Vn, JNET type 3 surface findings, or any other definitive sign of intramucosal or deeply invasive cancer. For this reason we proceeded with saline-immersion therapeutic endoscopy (SITE) facilitated PCM-ESD. Results After dissection of the distal part of the lesion, the MR sign was encountered within the submucosal pocket, underneath a large nodule. Despite continuing dissecting this severely fibrotic submucosal area using the PCM technique, increasing severity of submucosal fibrosis and repeated bleeding from convergent, irregular submucosal neovascularisation around the MR site (with an appearance akin to ‘solar flares’), impeded further resection. ESD was therefore discontinued due to high suspicion for submucosal invasion. Histopathological analysis of biopsies taken from the MR area confirmed deep submucosal invasion. Conclusions Our findings reinforce the suspicion that a flare of neovascularisation convergent onto the MR area is suggestive of deep submucosal invasion. In this scenario ESD could be discontinued and surgical options should be considered.