Amelanotic Anorectal Malignant Melanoma: Case Report with Immunohistochemical Study and Literature Review |
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| Authors: | Juan B. Laforga Canales Joan M. Gasent Blesa |
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| Affiliation: | aDepartment of Pathology, Hospital de Dénia, Denia, Spain;bDepartment of Oncology, Hospital de Dénia, Denia, Spain |
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| Abstract: | Epithelioid cell tumors presenting in the gastrointestinal tract are uncommon, but when they arise, arriving at a correct diagnosis is important. We report a case of anal malignant melanoma in an 82-year-old man who microscopically showed an epithelioid malignant tumor simulating a gastrointestinal stromal tumor. C-kit stain and Melan-A were diffusely and strongly positive, while HMB-45 was focally positive. This case illustrates the potential pitfall of relying on a single antibody or inadequate panel of immunohistochemical stains to confirm the diagnosis. We recommend to apply an adequate immunohistochemical panel which includes S-100 protein, HMB-45 and Melan-A in order to make an accurate diagnosis, and discuss the differential diagnosis and surgical treatment modalities.Key Words: Malignant melanoma, Rectum, Anus, Immunohistochemistry, Gastrointestinal stromal tumor |
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