Anal canal melanoma misdiagnosed and treated as prolapsed hemorrhoids in a male patient

SummaryMalignant melanoma of the anal canal is a rare, but aggressive, tumor with a poor prognosis. It represents less than 1% of all melanomas and 4% of anorectal tumors. We are reporting this case because of its rarity in men and because, in this instance, the tumor was misdiagnosed as prolapsed thrombosed hemorrhoids and excised. Examination showed a visible exophytic irreducible growth measuring about 3 × 3 cm and protruding outside the anal verge and involving the anterior two-thirds of the circumference of the anal canal. A biopsy sample showed round to oval cells with prominent nucleoli and marked intracytoplasmic pigmentation. A magnetic resonance imaging scan showed a tumor with nearly complete luminal obstruction and liver metastasis. The patient received chemotherapy and radiotherapy, but the response was very poor and he died 2 months later.