Endoscopic mesorectal dissection for precise pathologic staging and potential treatment of locally advanced rectal cancer.

Background and Aims: Traditional surgical techniques for rectal cancer resection may face limitations in accessing lesions at extreme rectal locations. Endoscopic mesorectal dissection (EMD) enables wide-margin resection without the constraints of conventional surgery. We present a case demonstrating the feasibility of EMD for accurate, organ-sparing staging of rectal cancer. A 67-year-old man with abdominal pain and positive Cologuard test (Exact Sciences Corporation, Madison, Wis, USA) results underwent colonoscopy that revealed a 2-cm sessile polyp 12 cm from the anal verge, removed with a hot snare. Pathology showed invasive adenocarcinoma with positive deep margins. Given challenges with low anterior resection and transanal total mesorectal excision, EMD was selected for precise staging. Methods: Endoscopy revealed a 15-mm postpolypectomy scar with nodularity. Lesion borders were marked, and methylene blue injection achieved partial lift. A circumferential incision exposed the muscularis propria, allowing full-thickness myotomy into the perirectal fat. The 35-mm lesion was dissected and retrieved en bloc, and the defect was closed with OverStitch sutures (Boston Scientific Corporation, Marlborough, Mass, USA). Results: Pathology confirmed pT2 adenocarcinoma with R0 margins. The patient had no adverse events, demonstrating the technical success of EMD in achieving en bloc R0 resection. Conclusions: EMD achieved en bloc R0 resection, highlighting its efficacy as a minimally invasive, organ-sparing approach for precise staging of rectal cancer.