Li YX, Guo LJ. Residual anorectal malignant melanoma presenting as polyp-like lesion detected during colonoscopic withdrawal observation: A case report and review of literature. World J Clin Cases 2026; 14(10): 119456 [DOI: 10.12998/wjcc.v14.i10.119456]
Corresponding Author of This Article
Lin-Jie Guo, MD, Associate Professor, Department of Gastroenterology, West China Hospital, Sichuan University, No. 37 Guoxue Alley, Wuhou District, Chengdu 610000, Sichuan Province, China. guolj08@163.com
Research Domain of This Article
Gastroenterology & Hepatology
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Case Report
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Apr 6, 2026 (publication date) through Apr 5, 2026
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Publication Name
World Journal of Clinical Cases
ISSN
2307-8960
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Baishideng Publishing Group Inc, 7041 Koll Center Parkway, Suite 160, Pleasanton, CA 94566, USA
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Li YX, Guo LJ. Residual anorectal malignant melanoma presenting as polyp-like lesion detected during colonoscopic withdrawal observation: A case report and review of literature. World J Clin Cases 2026; 14(10): 119456 [DOI: 10.12998/wjcc.v14.i10.119456]
Residual anorectal malignant melanoma presenting as polyp-like lesion detected during colonoscopic withdrawal observation: A case report and review of literature
Ya-Xin Li, Lin-Jie Guo
Ya-Xin Li, Lin-Jie Guo, Department of Gastroenterology, West China Hospital, Sichuan University, Chengdu 610000, Sichuan Province, China
Author contributions: Li YX contributed to manuscript writing and editing, and data collection; Li YX contributed to data analysis; Guo LJ contributed to conceptualization and supervision; and all authors have read and approved the final manuscript.
Informed consent statement: Informed written consent was obtained from the patient for publication of this report and any accompanying images.
Conflict-of-interest statement: All authors declare that they have no conflict of interest to disclose.
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).
Corresponding author: Lin-Jie Guo, MD, Associate Professor, Department of Gastroenterology, West China Hospital, Sichuan University, No. 37 Guoxue Alley, Wuhou District, Chengdu 610000, Sichuan Province, China. guolj08@163.com
Received: February 2, 2026 Revised: February 18, 2026 Accepted: March 10, 2026 Published online: April 6, 2026 Processing time: 62 Days and 0.5 Hours
Abstract
BACKGROUND
Anorectal mucosal melanoma (AMM) is a rare, aggressive malignancy with a poor prognosis. Early lesions are often small, amelanotic, and located in the endoscopic blind spots, leading to frequent missed diagnoses. This case highlights the importance of meticulous endoscopic surveillance in detecting early postoperative recurrence.
CASE SUMMARY
A 67-year-old man was followed up two months after surgical resection of perianal AMM. Routine forward-view colonoscopy revealed no abnormalities. Systematic withdrawal with rectal retroflexion identified a 0.5 cm sessile, white polyp adjacent to the surgical scar. Narrow-band imaging suggested benign features, but white-light endoscopy revealed punctate abnormal microvasculature. Biopsy and immunohistochemistry confirmed local recurrence of malignant melanoma. This case demonstrates that early, subtle recurrent lesions may mimic benign polyps and high-quality structured endoscopic examinations are required, including careful inspection of scar areas, retroflexion, and assessment of microvascular patterns, to confirm the diagnosis.
CONCLUSION
Systematic, meticulous endoscopic surveillance is critical for detecting early occult recurrence in high-risk AMM patients.
Core Tip: Anorectal mucosal melanoma (AMM) is rare, highly aggressive, and often presents with subtle or amelanotic lesions that are easily missed. We report a case of early local recurrence detected only through systematic colonoscopic withdrawal with rectal retroflexion and careful assessment of microvascular patterns. Despite appearing benign under narrow-band imaging, white-light endoscopy revealed suspicious lesions leading to biopsy-confirmed recurrence. This case highlights the critical role of meticulous, high-quality endoscopic surveillance in identifying early occult recurrence and underscores the need for individualized, standardized monitoring strategies in high-risk AMM patients.
