Primary Rectal Amelanotic Malignant Melanoma: A Rare Case Report.

Malignant melanoma of the rectum comprises 0.5%-4% of all anorectal cancers. Malignant melanoma of the rectum is exceptionally a rare disease. It commonly affects the fifth or sixth decade, with nonspecific symptoms such as rectal bleeding or anal pain. After skin and retina, anorectum is the third common site for malignant melanoma. Proper diagnosis is difficult in the majority of cases due to lack of pigmentation and amelanotic histological appearance. Prognosis is very poor with a median survival of 24 months and five-year survival of 10%-15%. Anorectal malignant melanomas disseminate along the submucosal planes, therefore complete resection at the time of diagnosis is usually not possible.