Lee C, Kim MH, Choi ET, Park IJ, Lim SB, Yoon YS, Kim CW, Lee JL, Park EJ. Spontaneous colonic transection following pathologic complete response to pembrolizumab in high microsatellite instability colorectal cancer: A case report and review of literature. World J Clin Cases 2025; 13(30): 110330 [DOI: 10.12998/wjcc.v13.i30.110330]
Corresponding Author of This Article
Min Hyun Kim, MD, Division of Colon and Rectal Surgery, Department of Surgery, University of Ulsan College of Medicine, Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 05505, South Korea. mhjerrykim@gmail.com
Research Domain of This Article
Surgery
Article-Type of This Article
Case Report
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
World J Clin Cases. Oct 26, 2025; 13(30): 110330 Published online Oct 26, 2025. doi: 10.12998/wjcc.v13.i30.110330
Spontaneous colonic transection following pathologic complete response to pembrolizumab in high microsatellite instability colorectal cancer: A case report and review of literature
Chungyeop Lee, Min Hyun Kim, Eu-Tteum Choi, In Ja Park, Seok-Byung Lim, Yong Sik Yoon, Chan Wook Kim, Jong Lyul Lee, Eun Jung Park
Chungyeop Lee, Min Hyun Kim, In Ja Park, Seok-Byung Lim, Yong Sik Yoon, Chan Wook Kim, Jong Lyul Lee, Eun Jung Park, Division of Colon and Rectal Surgery, Department of Surgery, University of Ulsan College of Medicine, Asan Medical Center, Seoul 05505, South Korea
Eu-Tteum Choi, Department of Nursing, Asan Medical Center, Seoul 05505, South Korea
Author contributions: Lee C and Kim MH contributed to the manuscript writing and editing and data collection; Lee C and Choi ET contributed to the data analysis; Kim MH contributed to the conceptualization and provided supervision; All authors read and approved the final manuscript.
Informed consent statement: Written informed consent was obtained from the patient for publication of this case report and any accompanying images. The patient provided consent specifically for the publication of clinical information and imaging findings. No personally identifiable information is included in the published images.
Conflict-of-interest statement: All authors declare no conflicts of interest.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Min Hyun Kim, MD, Division of Colon and Rectal Surgery, Department of Surgery, University of Ulsan College of Medicine, Asan Medical Center, 88, Olympic-ro 43-gil, Songpa-gu, Seoul 05505, South Korea. mhjerrykim@gmail.com
Received: June 11, 2025 Revised: July 4, 2025 Accepted: August 13, 2025 Published online: October 26, 2025 Processing time: 123 Days and 1.2 Hours
Abstract
BACKGROUND
High microsatellite instability (MSI-H) colorectal cancer (CRC), caused by deficient mismatch repair, accounts for about 15% of all CRC cases and is more common in right-sided tumors. While early-stage MSI-H CRC has a relatively good prognosis, advanced cases often respond poorly to standard chemotherapy. Immune checkpoint inhibitors, such as pembrolizumab, have shown strong and lasting effects in MSI-H CRC. Pembrolizumab is now approved as a first-line treatment for metastatic MSI-H CRC due to its superior outcomes compared to traditional chemotherapy.
CASE SUMMARY
A 44-year-old male with MSI-H transverse colon cancer presented with hematochezia, abdominal pain, and significant weight loss. Imaging revealed a bulky tumor with invasion of adjacent structures and multiple liver lesions. A diverting ileostomy was performed followed by 36 cycles of pembrolizumab. The patient achieved a clinical and radiologic complete response. One month after completing the treatment, the patient underwent laparoscopic right hemicolectomy. A spontaneous transection of the colon at the original tumor site was unexpectedly identified. Final pathology confirmed pathological complete response (ypT0N0) with fibrosis. The patient recovered well after surgery, and follow-up showed no evidence of recurrence.
CONCLUSION
Immune checkpoint inhibitors may cause delayed structural damage to bowel tissue even after apparent complete tumor regression.
Core Tip: We report here the first case of spontaneous colonic transection in a patient with high microsatellite instability colon cancer who achieved pathologic complete response after long-term pembrolizumab therapy. Despite no residual tumor on imaging or pathology, intraoperative findings revealed a discontinuity of the bowel at the original tumor site. Immune-mediated remodeling can compromise bowel integrity and may not be apparent on imaging. Clinicians should consider potential anatomic changes when planning surgery in patients treated with immunotherapy, even in the context of a complete response.
