Thin Membranous Connective Tissue Encasing the Superior Mesenteric Vessels as an Objective Landmark for Robotic D3 Lymphadenectomy in Right-sided Colon Cancer: A Histological Study and Intraoperative Video Review.

Objectives: This study aimed to histologically identify and validate a consistent perivascular membranous structure encasing the superior mesenteric vessels and to evaluate its intraoperative visibility as an objective landmark for standardizing robotic central (D3) lymphadenectomy with central vascular ligation in right-sided colon cancer (RSCC). Methods: This translational anatomic study comprised (i) cadaveric histology of the superior mesenteric artery and vein (n = 5), (ii) validation using surgical resection specimens from RSCC (n = 5), and (iii) retrospective review of non-edited intraoperative videos from 78 consecutive robotic D3 procedures. Two skill-qualified surgeons, who were blinded to pathological outcomes, independently graded visibility and assessed associations with body mass index (BMI) and surgeon experience. Results: Histology consistently showed a collagenous and elastic membranous layer encasing the superior mesenteric vessels and separating them from mesenteric lymphofatty tissue; this is termed the thin membranous connective tissue (TMCT). Of 78 cases, TMCT has clear visibility in 69 (88%) and poor visibility in 9 (12%), with no association with BMI ( Conclusions: TMCT, a histologically defined perivascular layer that is usually identifiable during robotic surgery, provides an objective boundary to delineate the optimal central dissection plane around the superior mesenteric vessels and supports safer, more reproducible robotic D3 lymphadenectomy for RSCC.