CASE REPORT article
Front. Oncol.
Sec. Surgical Oncology
Volume 15 - 2025 | doi: 10.3389/fonc.2025.1640063
This article is part of the Research TopicReal-World Clinical and Translational Research in Gastrointestinal CancersView all 12 articles
Rare primary anorectal malignant melanoma presenting with painless hematochezia: A case report
Provisionally accepted
- 1Department of General Surgery；The Institute of Translational Medicine, Second Affiliated Hospital of Nanchang University, Nanchang, China
- 2Health Examination Center, Second Affiliated Hospital of Nanchang University, Nanchang, China
- 3Department of General Surgery, Second Affiliated Hospital of Nanchang University, Nanchang, China
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Background: anorectal malignant melanoma (ARMM) is an exceedingly rare and highly aggressive malignancy characterized by low prevalence, high misdiagnosis rates, and frequent recurrence/metastasis. Case report: This report details the case of a 51-year-old female presenting with persistent bright red blood in stool. Digital rectal examination revealed a firm, spherical mass approximately 4 cm from the anal verge. Colonoscopy identified a pedunculated polypoid lesion (~2.5 cm in diameter) near the anorectal junction. Based on clinical symptoms, physical findings, and endoscopic features, a high suspicion of rectal cancer was initially raised. However, subsequent histopathological evaluation of biopsy specimens revealed immunohistochemical positivity for MelanA, S100, and Ki-67 (~30%), suggesting a probable diagnosis of malignant melanoma. After completing preoperative contrast-enhanced abdominal CT and pelvic MRI examinations and excluding surgical contraindications, the patient underwent laparoscopic-assisted abdominoperineal resection (Miles procedure) and postoperative adjuvant therapy with toripalimab. And no signs of recurrence were found during follow-up over 3 months postoperatively. Conclusion: This case underscores that ARMM can be clinically indistinguishable from rectal carcinoma, posing a high risk of misdiagnosis. It highlights the critical role of histopathology and immunohistochemistry (IHC) in definitive differentiation, emphasizing the necessity of accurate diagnosis through IHC.Finally, it demonstrates the evolving treatment paradigm from extensive surgery towards a multidisciplinary approach integrating radical resection with adjuvant immunotherapy, reflecting advances in molecular insights and ameliorated outcomes.
Keywords: case report, primary anorectal malignant melanoma, Hematochezia, laparoscopic-assisted abdominoperineal resection, treatment strategies
Received: 03 Jun 2025; Accepted: 31 Jul 2025.
Copyright: © 2025 Zhong, Zou, Peng, Hu and Xu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Xiaoyun Hu, Department of General Surgery, Second Affiliated Hospital of Nanchang University, Nanchang, China
Wei Xu, Department of General Surgery, Second Affiliated Hospital of Nanchang University, Nanchang, China
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