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Dae Ro Lim, Jung Cheol Kuk, Taehyung Kim, Hee Kyung Kim, Eung Jin Shin
(Division of Colon and Rectal Surgery, Department of Surgery, Soonchunhyang University College of Medicine, Soonchunhyang University Bucheon Hospital, Bucheon, South Korea)
Med Sci Case Rep 2018; 5:36-40
Malignant melanomas usually occur in the skin, retina, head, and neck regions. Anorectal malignant melanoma is a very rare colorectal disease, accounting for only 1–2% of all lower gastrointestinal cancer, 0.2–3% of all melanomas, and 4% of all anal malignancies. The correct diagnosis is confirmed using a combination of immunohistochemical stains for melanocytic differentiation, such as S-100, HMB-45, Melan-A, and tyrosinase.
CASE REPORT: We report the case of a 76-year-old South Korean woman with primary anorectal malignant melanoma confirmed after a laparoscopic-assisted abdominoperineal resection. She had a palpable anorectal mass 2.5 cm from the anal verge. No distant metastasis was found. The mass was a well-demarcated fungating mass (3.7×2.3×1.7 cm) in the anorectum. A histological examination showed a nesting or trabecular pattern of the epithelioid cells without melanin deposition. Immunohistochemical staining revealed that the tumor cells were positive for S-100 protein, Melan-A, and vimentin, confirming the primary anorectal amelanotic melanoma diagnosis.
CONCLUSIONS: Our patient underwent laparoscopic-assisted abdominoperineal resection to treat a rare anorectal malignant melanoma.