Successful Salvage Underwater Endoscopic Mucosal Resection for Early Colorectal Cancer with Unclear Horizontal and Vertical Margin after Cold Snare Polypectomy: Two Case Reports.

We sometimes encounter a case of early colorectal cancer with positive or unidentified margin after cold snare polypectomy (CSP). Case 1 was a 70-year-old woman who underwent total colonoscopy at our center. An 8-mm lesion classified as 0-IIa+IIc in the Paris classification was detected in the descending colon and removed with CSP. Case 2 was a 60-year-old man who underwent total colonoscopy at our center. A 6-mm lesion classified as 0-Is in the Paris classification was detected in the rectum and removed with CSP. Both lesions resulted in well-differentiated adenocarcinoma with unidentified horizontal and vertical margins pathologically. We safely performed underwater endoscopic mucosal resection (UEMR) for the post-CSP scar because residual cancer could not be ruled out completely. Pathological results showed that there was no residual cancer in either case. We report two cases of successful salvage UEMR for early colorectal cancer with unidentified horizontal and vertical margins after CSP. Salvage UEMR after CSP in the early stage may facilitate the exploration of residual cancer or the resection of residual cancer.