Histologic changes caused by injection of a novel submucosal lifting agent for endoscopic resection in GI lesions

Background and Aims: ORISE Gel is a recently introduced, U.S. Food and Drug Administration-approved submucosal lifting agent used in endoscopic resection of GI lesions. Histologically evident gel deposits in resected specimens may pose a potential diagnostic pitfall. To aid in recognition of this procedure-related artifact, we report the largest histologic series of ORISE Gel in endoscopic and surgical resection specimens to date.Methods: Fifty-eight EMR/endoscopic submucosal dissection (ESD) specimens with ORISE Gel injection and 5 interval surgical resection specimens with previous ORISE Gel injection were included. Patient demographics and endoscopy reports were obtained. Histologic slides from all cases were reviewed. Histochemical stains were performed on select cases.Results: Fifty-one EMR and 7 ESD specimens were identified. In 51 of 58 (88%) endoscopic resection specimens, amorphous, pale blue-gray, finely granular material was evident in the submucosa, as well as focally within the mucosa in 4 cases. Most cases showed homogeneous near-complete filling of the submucosa with this material, whereas a few demonstrated areas of condensation and retraction. Mucicarmine and periodic acid-Schiff stains were negative for mucin. Interval surgical resection specimens revealed extensive deposition of dense, eosinophilic material with associated multinucleated giant cells in the submucosa in all cases, with transmural extension in 3 cases.Conclusion: ORISE Gel injection during endoscopic resection of GI lesions results in deposition of amorphous, blue-gray material seen in histologic sections, whereas interval surgical resection specimens demonstrate dense, eosinophilic material with an associated giant cell reaction. Awareness of these artifacts will help avoid misinterpretation of their presence as pathologic findings.