Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report
BackgroundAnorectal malignant melanoma (ARMM) is an exceedingly rare and highly aggressive malignancy characterized by low prevalence, high misdiagnosis rates, and frequent recurrence/metastasis.Case reportThis report details the case of a 51-year-old woman presenting with persistent bright red bloo...
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Frontiers Media S.A.
2025-08-01
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| Series: | Frontiers in Oncology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fonc.2025.1640063/full |
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| author | Yuchun Zhong Yuchun Zhong Yueji Zou Long Peng Xiaoyun Hu Wei Xu Wei Xu |
| author_facet | Yuchun Zhong Yuchun Zhong Yueji Zou Long Peng Xiaoyun Hu Wei Xu Wei Xu |
| author_sort | Yuchun Zhong |
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| description | BackgroundAnorectal malignant melanoma (ARMM) is an exceedingly rare and highly aggressive malignancy characterized by low prevalence, high misdiagnosis rates, and frequent recurrence/metastasis.Case reportThis report details the case of a 51-year-old woman presenting with persistent bright red blood in her 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. Moreover, no signs of recurrence were found during follow-up over 3 months postoperatively.ConclusionThis 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 toward a multidisciplinary approach integrating radical resection with adjuvant immunotherapy, reflecting advances in molecular insights and ameliorated outcomes. |
| format | Article |
| id | doaj-art-8c75a33e1f614dbaadaf40163543f8c0 |
| institution | Kabale University |
| issn | 2234-943X |
| language | English |
| publishDate | 2025-08-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Oncology |
| spelling | doaj-art-8c75a33e1f614dbaadaf40163543f8c02025-08-20T05:32:44ZengFrontiers Media S.A.Frontiers in Oncology2234-943X2025-08-011510.3389/fonc.2025.16400631640063Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case reportYuchun Zhong0Yuchun Zhong1Yueji Zou2Long Peng3Xiaoyun Hu4Wei Xu5Wei Xu6Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, ChinaThe Institute of Translational Medicine, The Second Affiliated Hospital of Nanchang University, Nanchang University, Nanchang, Jiangxi, ChinaHealth Examination Center, The Second Affiliated Hospital of Nanchang University, Nanchang University, Nanchang, Jiangxi, ChinaDepartment of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, ChinaDepartment of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, ChinaDepartment of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, ChinaThe Institute of Translational Medicine, The Second Affiliated Hospital of Nanchang University, Nanchang University, Nanchang, Jiangxi, ChinaBackgroundAnorectal malignant melanoma (ARMM) is an exceedingly rare and highly aggressive malignancy characterized by low prevalence, high misdiagnosis rates, and frequent recurrence/metastasis.Case reportThis report details the case of a 51-year-old woman presenting with persistent bright red blood in her 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. Moreover, no signs of recurrence were found during follow-up over 3 months postoperatively.ConclusionThis 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 toward a multidisciplinary approach integrating radical resection with adjuvant immunotherapy, reflecting advances in molecular insights and ameliorated outcomes.https://www.frontiersin.org/articles/10.3389/fonc.2025.1640063/fullcase reportprimary anorectal malignant melanomahematochezialaparoscopic-assisted abdominoperineal resectiontreatment strategies |
| spellingShingle | Yuchun Zhong Yuchun Zhong Yueji Zou Long Peng Xiaoyun Hu Wei Xu Wei Xu Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report Frontiers in Oncology case report primary anorectal malignant melanoma hematochezia laparoscopic-assisted abdominoperineal resection treatment strategies |
| title | Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report |
| title_full | Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report |
| title_fullStr | Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report |
| title_full_unstemmed | Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report |
| title_short | Rare primary anorectal malignant melanoma presenting with painless hematochezia: a case report |
| title_sort | rare primary anorectal malignant melanoma presenting with painless hematochezia a case report |
| topic | case report primary anorectal malignant melanoma hematochezia laparoscopic-assisted abdominoperineal resection treatment strategies |
| url | https://www.frontiersin.org/articles/10.3389/fonc.2025.1640063/full |
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