Enhanced endoscopic transillumination enables precise tumor delineation in laparoscopic-endoscopic cooperative surgery for duodenal neuroendocrine tumor

A 21-year-old woman presented with melena. Gastroscopy revealed a protruding lesion in the descending duodenum. Endoscopic ultrasonography showed a ~2.0 × 1.9 cm hypoechoic mass originating from the muscularis propria ([ Fig. 1 ]). Given the deep location, laparoscopic-endoscopic cooperative surgery (LECS) was selected for full-thickness resection. Fig. 1 a Gastroscopy identified a protruding lesion in the descending duodenum. b Endoscopic ultrasound revealed a hypoechoic mass, measuring approximately 2.0 × 1.9 cm, within the muscularis propria. After Kocher maneuver, the gastroscope was positioned at the tumor. Endoscopic enhanced transillumination (Olympus, TRANSILLUM Mode) clearly illuminated the intestinal segment, outlining the entire tumor contour and margins ([ Video 1 ]), enabling precise co-localization. The resection area was marked 3 mm outside the border. Following laparoscopic resection ([ Fig. 2 ]), the duodenum was sutured in layers. Final gastroscopy confirmed no bleeding, normal papilla, and no stenosis. The operative time was 40 minutes with minimal blood loss. Pathology confirmed an R0 resection of a 19 × 16 × 6 mm NET G1 ([ Fig. 3 ]). The patient recovered uneventfully. Download Video Enhanced endoscopic transillumination provides clear delineation of tumor margins in a duodenal NET, facilitating a conservative and precise resection via the LECS approach. LECS, laparoscopic-endoscopic cooperative surgery; NET, neuroendocrine tumor.Video 1 Fig. 2 The tumor was completely resected laparoscopically. Fig. 3 a A macroscopic view of the 19 × 16 × 6 mm specimen. b H&E staining reveals nests of epithelioid cells in the lamina propria, consistent with a neuroendocrine tumor, G1. LECS is a feasible, safe approach for duodenal tumors [ 1 ]. However, determining serosal-side resection margins is challenging, and excessive resection risks stenosis. Although existing transillumination techniques have been documented [ 2 ], they often provide suboptimal illumination for defining the complete tumor margins. This case demonstrates that the novel application of enhanced endoscopic transillumination enabled precise tumor delineation without compromising laparoscopic lighting, thereby facilitating a conservative yet precise resection and establishing a safe and effective visualization strategy for duodenal neuroendocrine tumors. Endoscopy_UCTN_Code_TTT_1AT_2AD Publication History Article published online: 24 February 2026 © 2026. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/). Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany